# QiLing Tools — Free Online PDF, Image, Audio, Video, Mind Map & JSON Tools > QiLing Tools is a free online toolbox: merge and split PDFs, compress and convert images, trim and convert audio, compress video and make GIFs, plus an online mind map editor (QiLing Mind). Everything runs locally in your browser. No uploads, no sign-up. - URL: https://qilingtools.com/en - Last updated: 2026-10-29 - Price: Free, no sign-up - Privacy: Runs locally in the browser; files are never uploaded ## Categories - [PDF Tools](https://qilingtools.com/en/pdf) (76): Work with PDFs for free in your browser: merge files, split or extract pages, delete and reorder pages, rotate, convert to and from images, compress, watermark, add page numbers, sign or stamp, lay several pages per sheet, extract text, add text, headers and footers, redact, insert pages, turn PDFs into one long image, flatten forms, compare PDFs, edit bookmarks, impose booklets, OCR scans into searchable PDFs apply letterheads, convert PDF to Word and PowerPoint, inspect PDF info, make dark-mode PDFs remove blank pages, convert PDF to Excel, annotate, manage attachments, sanitize PDFs, create fillable forms, print posters, split by bookmarks or size and convert PDF to Markdown, Markdown to PDF, interleave double-sided scans PDF to EPUB, Bates numbering, scan deskew, page labels PDF ↔ CBZ, PDF to HTML PDF read-aloud, scanned-look effects, splitting book spreads, PDF to SVG, margins, watermark removal, repair, lossless optimization, font extraction, TOC pages, link editing, accessibility checks, form mail merge, word counts, print preflight, QR stamping, signature verification, invoice data extraction, content-based renaming and separator-page splitting. No uploads, fully private. - [Image Tools](https://qilingtools.com/en/image) (116): Edit images for free in your browser: batch compress, resize, convert between JPG/PNG/WebP, add text watermarks, stitch screenshots, remove backgrounds with AI, adjust colours, pixelate private details, split into grids, strip EXIF/GPS data, pick colours, make favicons, ID photos and GIFs, compress to an exact size, convert HEIC, beautify screenshots, turn photos into sketches, add text, blur backgrounds, scan QR codes, change DPI, extract text with OCR, make ID card copies, upscale with AI, scan documents, remove watermarks, replace colours, extract colour palettes, turn text into images, resize for social media, inspect image info and EXIF lay out photo prints, generate app icons, create e-signatures, edit GIFs, build CSS sprites, apply photo filters, add camera info frames, convert images to SVG, reduce photo noise dither images for thermal printers, blur faces automatically, auto-enhance photos, create oil paintings and tilt-shift miniatures, hide text in images, smart-crop to any ratio, and create duotone, halftone, glitch and double exposure effects, add sticker outlines, straighten tilted photos, mirror images, build photo mosaics, make cross-stitch patterns, adjust curves, apply LUTs, simulate colour blindness, extract line art, make jigsaw puzzles, memes, cartoon effects, wallpapers, avatars, screenshot annotation, placeholder images EXIF editing, panorama stitching color transfer, text-behind-subject effects, handwriting pages, portrait retouching, film negative conversion, duplicate photo finding, HDR, pixel sorting, seamless tiles, procedural textures, drawing grids, device mockups, feed planning, sprite animation, logos, shape collages, poster printing and a batch processing pipeline. Processed locally, never uploaded. - [Audio Tools](https://qilingtools.com/en/audio) (50): Process audio for free in your browser: convert MP3/WAV/AAC/FLAC/OGG, trim by time, merge and split clips, mix several tracks, reduce noise, strip silence, fade in and out, normalize loudness, shape the tone with a 3-band EQ, change speed and pitch, reverse, turn audio into a video with a cover image, render waveform images, record from the mic, edit ID3 tags, run a metronome, generate tones, detect BPM, render spectrograms, remove vocals, make ringtones, create 8D audio, apply voice effects, play a virtual piano and mix ambient sounds, fix audio channels and measure loudness, tune instruments, meter sound levels program drum beats, compress and limit audio make LRC lyrics, generate retro sound effects, play MIDI files turn humming into MIDI, make podcast audiograms and explore chords, scales and the circle of fifths, make seamless loops, decode DTMF and Morse, and run ABX blind tests. Powered by FFmpeg running locally, no uploads. - [Video Tools](https://qilingtools.com/en/video) (54): Process video for free in your browser: compress size, convert MP4/WebM, trim by time, merge clips, change speed, reverse, loop, fade in and out, color-correct, remove logos, picture-in-picture, add text or logo watermarks, burn SRT subtitles, crop the frame, rotate and flip, swap the soundtrack, convert to and from GIF, extract audio, capture frames, export frame sequences, change resolution and aspect ratio, stack videos side by side, record the screen, add text overlays, make contact sheets, compress to a target size, turn photos into slideshows, stabilize shaky footage, inspect media info, key out green screens, split videos, change frame rates, apply LUTs, remove sound, extract embedded subtitles edit subtitles design video covers, record from a webcam, make time-lapses blur faces in video, cut silences automatically, compare videos convert to animated WebP/APNG, detect scene cuts, make text videos auto-reframe to vertical, make countdown and lyrics videos, and add zoom and pan effects. Processed locally, fully private. - [Math Tools](https://qilingtools.com/en/math) (109): Over 30 free math tools in your browser: type a formula and graph it (functions, parametric and polar curves, data fitting, roots and extrema), plus a scientific calculator, equation solver, inequality solver, linear systems, regression, logarithms, conic sections, number theory, a Bézier curve editor, a LaTeX equation editor, confidence intervals and hypothesis tests, eigenvalues, Bayes’ theorem, Pascal’s triangle, derivatives and integrals, geometry and triangle solvers, trigonometry, statistics and probability distributions, combinations, matrices, sequences, fractions, percentages, ratios, complex numbers, unit conversion, interest, coordinate geometry, vectors, polynomials, set operations, truth tables, sudoku, GPA, significant figures, long division, arithmetic worksheets, mortgages, China income tax, 3D surface plots, Taylor series, a geometry sketchpad, a probability simulator, time calculator, discounts, step-by-step matrices, limits, function analysis, mental math practice, times tables, angle conversion, radicals, decimal ↔ fraction, big-number math, scale calculation, step-by-step derivatives, linear programming, graph algorithms, normal tables, box plots, a China salary calculator, step-by-step integrals, differential equations, Fourier series and FFT, sample size, IRR/NPV analysis, game theory, classical ciphers, fractals, Markov chains, the 24 game, an abacus, telling time, fraction visuals, polyhedra, linear transforms, domain coloring, CLT simulations, chi-square and ANOVA, FIRE planning and matrix decompositions. Everything runs locally. - [Chemistry Tools](https://qilingtools.com/en/chemistry) (68): Free chemistry tools in your browser: balance chemical equations, molar mass and mass percent, interactive periodic table, pH, titration curves, gas laws, solution concentration and dilution, stoichiometry and limiting reagents, empirical formulas, electron configuration, VSEPR shapes, enthalpy and Gibbs free energy, ICE tables, Nernst equation, oxidation numbers and half-life. Everything is computed locally. - [Physics Tools](https://qilingtools.com/en/physics) (196): Free physics tools in your browser: physics formula calculator, projectile motion, pendulum and spring oscillators, collisions and momentum, orbits, lenses and refraction, wave superposition and standing waves, Doppler effect, electric fields, resistor color codes, RC and DC circuits, magnetic fields and induction, charged particles, diffraction and polarization, heat conduction and engine cycles, kinetic theory, fluids, rotation and circular motion, simple machines, the Schrödinger equation, nuclear binding energy, force diagrams and beams, capacitors, logic circuits, room acoustics, color mixing, eye optics, rockets, Lagrange points, chaos, Chladni patterns, error propagation, physical constants and dimensional analysis, the Ising model, Brownian motion, materials, the HR diagram, cosmology, black holes, the solar system, EM waves and polarization, semiconductors, op-amps, capillarity, radiation dose, gyroscopes, tides, DC motors, AC power, Gauss's law, wave pulses, lasers, particle physics, entropy, Earth's energy balance, energy tracks, relative motion, motion graphs, normal modes, fiber optics, telescopes, hydrogen orbitals, X-rays, the Coriolis effect, car braking, the Magnus effect, the atmosphere, water waves, earthquakes, rainbows, sky color, solar and wind power, batteries, magnetic materials, guitar strings, phase diagrams, static electricity and lightning, the Smith chart, antennas, flight, skydiving, hot-air balloons, g-forces, biomechanics, exoplanets, eclipses, moon phases, planetary gravity, thin-film interference, the photoelectric effect, camera depth of field and exposure, scuba diving, gravitational waves, gravity assists, geomagnetism and aurorae, superconductivity, wire voltage drop, thermal expansion, heat pumps, the brachistochrone, sonar and radar, nuclear reactors, polarization, microscopes, a ripple tank, wind instruments, neutron stars, GPS, the space elevator, reentry, fusion, MRI, hydropower, the power grid, a virtual wind tunnel, truss analysis, a live sky chart, sundials, asteroid impacts, wireless charging, microwave ovens, Tesla coils, loudspeakers, trebuchets, archery, bicycles, sailing, earthquake-resistant buildings, harmonographs, non-Newtonian fluids, vernier caliper reading, ticker-tape analysis, meter conversion, conveyor-belt problems, an oscilloscope, transistors, the 555 timer, sampling and aliasing, spin, quantum statistics, pendulum waves, hurricanes, volcanoes, radio propagation, household wiring, circuit dynamics, sliding-rod induction, the Hall effect and mass spectrometer, momentum models, gas columns, wave graphs, phase changes, the Cavendish, Millikan, Rutherford and Franck–Hertz experiments, the speed of light, holography, vertical circular motion, satellite orbit changes, connected bodies, vehicle start-up, charged-particle deflection, bounded magnetic fields, combined fields, solar sails, pressure, density measurement, electromagnets, Ohm's law experiments, plane mirrors, the convex-lens experiment, special relativity and blackbody radiation. Interactive simulations that run locally. - [Productivity](https://qilingtools.com/en/office) (93): Free productivity tools in your browser: QiLing Mind mind maps with XMind and Markdown import/export, date difference and age calculator, stopwatch, countdown and Pomodoro timer, world clock and time zone converter, text cleanup and bulk find & replace, random name picker and team generator, BMI calculator, barcode generator, text to speech, password generator, QR codes, word count, case conversion, line sorting, Chinese pinyin, Simplified/Traditional Chinese conversion, a chart maker, a Chinese lunar calendar, a typing test, Morse code, a spin-the-wheel picker, an online notepad, a bill splitter, day countdowns, a kanban board, flashcards, an emoji picker, invoices and receipts, a resume builder, word clouds, a password checker, speech to text, a teleprompter, a whiteboard and a habit tracker, spreadsheet, Gantt chart, flowchart maker, calendar maker, WeChat article formatter, timetable, certificate maker unit price comparison, copybooks, seating charts, envelope and label printing, business cards, styled QR codes ID number validation, batch renaming, graph and music paper, planners, word search and crossword puzzles, bingo cards, Markdown slides, an expense tracker, a decision matrix, email signatures, invitation cards, text analysis, a meeting planner, reading speed and brain tests, shift rosters, a gift ledger, document templates, a ZIP compressor and extractor, a RAR / 7Z extractor, a ZIP password tool, a tar / tar.gz packer, a large-file splitter, Excel to CSV / JSON, Word to Markdown, PowerPoint to outline and notes, TXT to EPUB, and EPUB text extraction and metadata editing. Runs locally, nothing is uploaded. - [Developer Tools](https://qilingtools.com/en/dev) (93): Free developer tools in your browser: JSON formatter and validator, CSV ↔ JSON, JSON to TypeScript/Go, SQL formatter, Markdown table generator, Base64/URL/Unicode encoding, URL parser, JWT decoder, timestamps, hashes, UUIDs, regex tester, text diff, IPv4 subnet calculator, chmod calculator, User-Agent parser, HTTP status codes, cron expressions, YAML ↔ JSON, XML and CSS formatters, JSON diff, JSONPath, text encryption (AES/RSA/HMAC), CSS gradient and shadow generators, curl to code, HTML formatter, JWT generator, keycode inspector, mock data generator, WebSocket tester, JS formatter, JSON Schema tools, meta tag generator, .gitignore generator, HTTP client, docker run ↔ compose, Nginx config generator, string escaping and SVG optimizer, color contrast checker, regex visualizer, encoding converter, semver tool, code screenshots, certificate decoder, TOTP, password hashing HTML ↔ Markdown, TOML/INI/.env conversion, CSS clip-path, a Flex/Grid playground, Tailwind palettes robots.txt / sitemap generators, an OpenAPI viewer, IPv6 calculator, text tables, htpasswd, JSON to SQL, a sorting visualizer, XPath tester, binary decoder, security headers checker, hex viewer, license picker, Kubernetes YAML, systemd units, SSH keys, a palette generator, CSS animations, SVG shapes, a GraphQL formatter, a JSON graph viewer, SQL on CSV, file MD5 / SHA-256 checksums and an invisible character detector. Runs locally, nothing is uploaded. ## All tools ### PDF Tools - [Merge PDF](https://qilingtools.com/en/pdf/merge): Free online PDF merger: combine several PDF files into one in the order you choose, with reordering. Processed locally in your browser, no upload, no sign-up. - [Split / Extract PDF](https://qilingtools.com/en/pdf/split): Free online PDF splitter: extract a page range into a new PDF, or split every page into its own file and download them as a ZIP. Processed locally. - [Rotate PDF](https://qilingtools.com/en/pdf/rotate): Free online PDF rotator: rotate all or selected pages by 90°, 180° or 270° to fix scanned documents. Processed locally, no upload. - [PDF to Image](https://qilingtools.com/en/pdf/to-image): Free online PDF to image converter: render every page as a high-resolution JPG or PNG at 72/150/300 DPI, download all as a ZIP. Processed locally, no upload. - [Image to PDF](https://qilingtools.com/en/pdf/from-image): Free online image to PDF converter: combine JPG, PNG and WebP images into one PDF in order, with A4 or image-sized pages. Processed locally, no upload. - [Compress PDF](https://qilingtools.com/en/pdf/compress): Free online PDF compressor: re-render pages with compressed images to shrink scanned and image-heavy PDFs, with adjustable quality. Processed locally. - [Watermark PDF](https://qilingtools.com/en/pdf/watermark): Free online PDF watermark tool: add text watermarks to every page, tiled or centred, with opacity and angle controls. Any language, processed locally. - [Delete PDF Pages](https://qilingtools.com/en/pdf/delete): Free online tool to delete PDF pages: remove pages by number or range and keep the rest, then download. Processed locally, no upload. - [Extract PDF Text](https://qilingtools.com/en/pdf/extract-text): Free online PDF text extractor: pull all text from a text-based PDF page by page, copy it or download as TXT. Parsed locally, never uploaded. - [Organize PDF Pages](https://qilingtools.com/en/pdf/organize): Free online PDF page organizer: every page as a thumbnail — drag to reorder, rotate or delete single pages, then export a new PDF. Runs locally. - [Add Page Numbers to PDF](https://qilingtools.com/en/pdf/page-number): Free online PDF page numbering tool: add page numbers choosing the position, style, font size, starting number, page range and custom template. Runs locally. - [Sign & Stamp PDF](https://qilingtools.com/en/pdf/sign): Free online PDF signing tool: drop in a handwritten signature or company stamp, drag it into place on a page preview, adjust size and opacity, then export. - [PDF Cross-Page Seal](https://qilingtools.com/en/pdf/cross-seal): Stamp a cross-page seal on a PDF for free: the seal is sliced by page count, one slice per page edge, so fanned pages rebuild it and no page can be swapped. - [PDF Editor](https://qilingtools.com/en/pdf/edit): Free online PDF editor: click text on the page to change or delete it, with the old text truly removed and the rest of the page untouched. Add text, images and cover boxes too. - [Multiple Pages per Sheet](https://qilingtools.com/en/pdf/n-up): Free online PDF N-up tool: lay 2, 4, 6 or 9 pages onto one sheet with a choice of A4 orientation, margins and gaps to save paper. Runs locally, never uploaded. - [Crop PDF](https://qilingtools.com/en/pdf/crop): Free online PDF cropper: detect each page's content area and trim the white space, or set margins by hand with a live preview. Stays vector, text selectable. - [Encrypt PDF](https://qilingtools.com/en/pdf/encrypt): Free online PDF encryption: set an open password and restrict printing, copying, editing and annotating with AES-256. Everything runs on your device. - [Unlock PDF](https://qilingtools.com/en/pdf/decrypt): Free online PDF unlocker: enter the password you already know and export a PDF without it, or lift owner-only limits on printing and copying. Runs locally. - [Extract PDF Images](https://qilingtools.com/en/pdf/extract-images): Free online PDF image extractor: pull embedded pictures out at their original resolution as PNG or JPG, with fragment filtering and duplicate removal. - [Resize PDF Pages](https://qilingtools.com/en/pdf/resize): Free online PDF page resizer: put mixed-size pages onto one paper size — A4, A3, Letter or custom — scaled proportionally and centred, with optional margins. - [Edit PDF Properties](https://qilingtools.com/en/pdf/metadata): Free online PDF metadata editor: view and change the title, author, subject and keywords, or wipe every property and timestamp for privacy. Runs locally. - [PDF to Black & White](https://qilingtools.com/en/pdf/grayscale): Free online PDF grayscale converter: turn a colour PDF into grayscale or pure black and white, with adjustable threshold, brightness and live preview. - [Add Text to PDF](https://qilingtools.com/en/pdf/add-text): Free online tool to add text to a PDF: click the page to type, then drag, resize, recolour or bold it. Chinese supported and the pages stay vector. - [Flatten PDF](https://qilingtools.com/en/pdf/flatten): Free online PDF flattener: lists every form field so you can fill it in first, then turns the form into plain page content, optionally rasterizing each page. - [PDF Header & Footer](https://qilingtools.com/en/pdf/header-footer): Free online tool to add headers and footers to a PDF: text left, centre or right with {page}, {total}, {date} and {filename} variables, plus a separator line. - [Insert Pages into PDF](https://qilingtools.com/en/pdf/insert): Free online tool to insert pages into a PDF: add blank pages, images or pages from another PDF at the start, the end or around page N, or interleave two scans. - [Redact PDF](https://qilingtools.com/en/pdf/redact): Free online PDF redaction: draw boxes over names, ID numbers or amounts and black them out for good — those pages are re-rendered so the text is gone. - [PDF to Long Image](https://qilingtools.com/en/pdf/to-long-image): Free online PDF to long image converter: stack the pages you pick into one tall JPG or PNG, with adjustable width, gap and background. Huge results auto-split. - [Photo Print Layout](https://qilingtools.com/en/image/print-layout): Free online photo print layout: tile ID photos at 300 DPI onto 4×6, 5×7, A4 or Letter paper with gaps, cut lines and copies, then export JPG or PDF. - [PDF Booklet Maker](https://qilingtools.com/en/pdf/booklet): Free online PDF booklet maker: reorder pages for saddle-stitch printing, two up on landscape sheets padded to a multiple of four, duplex or separate sides. - [PDF Bookmarks Editor](https://qilingtools.com/en/pdf/bookmarks): Free online PDF bookmark editor: read the outline, then add, rename, nest and reorder bookmarks, set pages by clicking thumbnails, or paste a table of contents. - [Compare PDF](https://qilingtools.com/en/pdf/compare): Free online PDF compare: see every added and removed word highlighted page by page, plus a pixel diff that boxes changed images and layout in red. - [PDF OCR](https://qilingtools.com/en/pdf/ocr): Free online PDF OCR: recognise English, Chinese and digits in scanned PDFs in your browser and add an invisible text layer, so pages become searchable. Local. - [PDF Overlay & Letterhead](https://qilingtools.com/en/pdf/overlay): Free online PDF overlay tool: put a letterhead, background, watermark or stamp behind or in front of every page, with page range, scaling and opacity. - [PDF Dark Mode](https://qilingtools.com/en/pdf/dark-mode): Free online PDF dark mode converter: turn black-on-white PDFs into light-on-dark pages, with hue-preserving, sepia or custom colours. Text stays selectable. - [PDF Info & Inspector](https://qilingtools.com/en/pdf/info): Free online PDF inspector: version, page count and sizes, metadata, encryption, permissions, fonts, images, form fields and attachments, as a JSON report. - [Remove Blank Pages from PDF](https://qilingtools.com/en/pdf/remove-blank): Free online tool to remove blank pages from a PDF: it finds empty and near-blank scans, marks them on thumbnails you can toggle, sensitivity adjustable. - [PDF to PowerPoint](https://qilingtools.com/en/pdf/to-ppt): Free online PDF to PowerPoint converter: every page becomes a high-resolution slide in a real .pptx, sized to the page or 16:9, with the text as speaker notes. - [PDF to Word](https://qilingtools.com/en/pdf/to-word): Free online PDF to Word converter: turn a PDF into an editable .docx keeping paragraphs, headings, bold and italic, lists, images and page breaks. Runs locally. - [Annotate PDF](https://qilingtools.com/en/pdf/annotate): Free online PDF annotator: highlight, draw, add shapes, arrows, sticky notes and text boxes, then save as editable annotations or flatten them. Runs locally. - [PDF Attachments](https://qilingtools.com/en/pdf/attachments): Free PDF attachment manager: list embedded files with size and description, download one or all as ZIP, attach new files or remove old ones. Runs locally. - [Sanitize PDF](https://qilingtools.com/en/pdf/sanitize): Free PDF sanitizer: find and remove JavaScript, auto-run and launch actions, links, attachments, comments, forms and metadata, with a before/after report. - [PDF to Excel](https://qilingtools.com/en/pdf/to-excel): Free PDF to Excel converter: detects ruled and borderless tables, lets you adjust columns, turns numbers into real values and exports XLSX or CSV. Runs locally. - [Create PDF Form](https://qilingtools.com/en/pdf/create-form): Make any PDF fillable: draw text fields, checkboxes, radio buttons, dropdowns, date and signature fields; set names, required flags and tab order. Free, local. - [PDF Poster Printing](https://qilingtools.com/en/pdf/poster): Enlarge a PDF page and tile it across A4, A3 or Letter sheets with overlap, crop marks, A1/A2 labels and an assembly guide. Vector output, free and local. - [Advanced PDF Splitter](https://qilingtools.com/en/pdf/split-advanced): Split a PDF by bookmarks, maximum file size, every N pages, odd/even pages, blank separator pages or a keyword/regex. Preview the parts, download a ZIP. - [PDF to Markdown](https://qilingtools.com/en/pdf/to-markdown): Convert PDF to clean Markdown for ChatGPT, Claude and other LLMs: headings, lists, bold/italic, GFM tables and links, minus headers and footers. - [Markdown to PDF](https://qilingtools.com/en/pdf/from-markdown): Convert Markdown or plain text to PDF online with a live paginated preview, three themes, paper and margin options, headers, page numbers and a TOC. - [Merge Scanned Fronts & Backs](https://qilingtools.com/en/pdf/interleave): Combine a fronts PDF and a backs PDF from a single-sided scanner into correct duplex order, with reversed backs, 180° rotation, blank padding and preview. - [PDF to EPUB](https://qilingtools.com/en/pdf/to-epub): Convert PDF to a reflowable EPUB 3 e-book online: rebuilt paragraphs and headings, chapters from bookmarks, no headers or footers, images, cover and metadata. - [Bates Numbering](https://qilingtools.com/en/pdf/bates): Add Bates numbers to PDFs: prefix, suffix, zero padding, numbering continued across files, 6 positions, white box, files renamed by range plus a CSV index. - [PDF ⇄ CBZ Comics](https://qilingtools.com/en/pdf/cbz): Convert comics both ways: PDF to CBZ with lossless page extraction, CBZ/ZIP to PDF with natural sort, A4/B5 fit and manga order, images to CBZ + ComicInfo.xml. - [Deskew PDF](https://qilingtools.com/en/pdf/deskew): Straighten skewed scanned PDFs and images: per-page skew detection (±15°, 0.1° steps), before/after preview, manual override, border removal, original sizes. - [PDF Page Labels](https://qilingtools.com/en/pdf/page-labels): Edit PDF page labels: decimal, Roman, letter or prefix-only ranges with custom start numbers. Reads existing labels and previews every page’s label. - [PDF Read Aloud](https://qilingtools.com/en/pdf/read-aloud): Listen to a PDF read aloud sentence by sentence, highlighted in the text and on the page. Choose voices and speed, click to jump, and resume later. - [PDF to HTML](https://qilingtools.com/en/pdf/to-html): Convert PDF to HTML: semantic reflowable pages with headings, lists, tables and images, or a fixed layout with selectable text. Single file or ZIP. - [Add PDF Margins](https://qilingtools.com/en/pdf/margin): Add margins and a binding gutter to PDF pages: per side in mm, in or pt, mirrored for duplex, enlarge page or shrink content, background color, cut lines. - [Scanned Look PDF](https://qilingtools.com/en/pdf/scan-effect): Give a digital PDF a scanned or photocopied look: seeded random tilt, grayscale or color, paper tint, grain, blur, toner specks, edge shadow and live preview. - [Split PDF Spreads](https://qilingtools.com/en/pdf/split-spread): Split book-spread scans into single pages: left/right or top/bottom, auto gutter detection with per-page tweaks, right-to-left order, no recompression. - [PDF to SVG](https://qilingtools.com/en/pdf/to-svg): Convert PDF pages to SVG: paths, colors, gradients and patterns stay vector, text stays editable, images embedded. Image + text-layer mode, SVG or ZIP. - [PDF Fonts](https://qilingtools.com/en/pdf/fonts): See which fonts a PDF uses: type, embedding, subset, encoding and ToUnicode per page, with copy/search warnings. Extract embedded fonts as TTF, OTF, CFF or PFB. - [Optimize PDF](https://qilingtools.com/en/pdf/optimize): Losslessly shrink PDFs: merge duplicate fonts and images, Flate-compress streams, pack object streams, drop unused data, optionally downsample big images. - [Remove PDF Watermark](https://qilingtools.com/en/pdf/remove-watermark): Remove watermarks from your own PDFs: detects watermark annotations, layers, artifacts and text or images repeated on each page, then deletes them cleanly. - [PDF Find and Replace](https://qilingtools.com/en/pdf/find-replace): Find and replace text in a PDF for free: fix dates, names, prices or typos, or delete text. Old text is truly removed and the rest stays put. Runs locally. - [Repair PDF](https://qilingtools.com/en/pdf/repair): Fix corrupt PDFs that won’t open: diagnoses header, xref, trailer and truncation problems, rebuilds the xref and page tree, re-renders as a last resort. Free. - [PDF Table of Contents](https://qilingtools.com/en/pdf/toc): Create a clickable table of contents page for a PDF from bookmarks or detected headings: editable levels and pages, dotted leaders, links that stay correct. - [PDF Accessibility Checker](https://qilingtools.com/en/pdf/accessibility): Check PDF accessibility: tags, language, title, fonts, alt text, headings, form tooltips, links and scanned pages. Apply safe fixes and export a report. - [PDF Form Mail Merge](https://qilingtools.com/en/pdf/form-merge): Fill a PDF form from CSV rows: auto-matched fields, checkboxes, radios, dropdowns, CJK text, optional flattening, one PDF per row or combined; export form data. - [PDF Link Manager](https://qilingtools.com/en/pdf/links): List every link in a PDF with its anchor text, export CSV, check URL format, edit or delete links, draw new links and auto-link plain-text URLs and emails. - [PDF Word Count](https://qilingtools.com/en/pdf/word-count): Count PDF words Word-style for English and CJK: characters, sentences, paragraphs, per-page chart, reading time, keywords and Flesch readability score. - [PDF Preflight Check](https://qilingtools.com/en/pdf/preflight): Free online PDF preflight: bleed and TrimBox, effective image DPI, RGB/CMYK/spot colors, fonts, transparency, overprint, hairlines and print permission. - [Add QR Codes to PDF](https://qilingtools.com/en/pdf/qr-stamp): Stamp a QR code on every PDF page: content from page number, file name, date or your own ID, drawn as crisp vectors, upright on rotated pages, batch files. - [PDF Signature Verifier](https://qilingtools.com/en/pdf/signatures): Verify PDF digital signatures: recompute digests, check RSA/ECDSA signatures, view the certificate chain, timestamps and LTV data, and spot edits after signing. - [Chinese E-Invoice Extractor](https://qilingtools.com/en/pdf/invoice): Batch-extract Chinese VAT and digital e-invoice PDFs: number, date, buyer, seller, tax IDs, amounts, line items; QR cross-check, duplicates, CSV. - [Rename PDFs by Content](https://qilingtools.com/en/pdf/rename): Batch rename PDFs by content: put dates, invoice or order numbers, emails, totals, titles or labelled text into a name pattern; preview clashes. - [Split PDF by Separator Sheets](https://qilingtools.com/en/pdf/split-qr): Split a batch-scanned PDF at QR or barcode separator sheets, blank pages or marker text; keep or drop separators, name files from QR, print sheets. ### Image Tools - [PDF to Image](https://qilingtools.com/en/pdf/to-image): Free online PDF to image converter: render every page as a high-resolution JPG or PNG at 72/150/300 DPI, download all as a ZIP. Processed locally, no upload. - [Image to PDF](https://qilingtools.com/en/pdf/from-image): Free online image to PDF converter: combine JPG, PNG and WebP images into one PDF in order, with A4 or image-sized pages. Processed locally, no upload. - [Compress Image](https://qilingtools.com/en/image/compress): Free online image compressor: batch compress JPG, PNG and WebP with adjustable quality and a max size, showing the before and after sizes. Runs locally. - [Resize Image](https://qilingtools.com/en/image/resize): Free online image resizer: batch resize by pixel width and height or by percentage with the aspect ratio locked. JPG, PNG and WebP, processed locally. - [Convert Image](https://qilingtools.com/en/image/convert): Free online image converter: batch convert JPG, PNG, WebP, GIF and BMP images to JPG, PNG or WebP. Processed locally, no upload. - [Watermark Image](https://qilingtools.com/en/image/watermark): Free online image watermark tool: batch add text watermarks with position, tiling, opacity, size and color settings. Processed locally, no upload. - [Stitch Images](https://qilingtools.com/en/image/stitch): Free online image stitcher: join screenshots or photos vertically or horizontally into one long image, with gap and background options. Processed locally. - [Remove Background](https://qilingtools.com/en/image/remove-bg): Free online background remover: AI finds people, products and animals and cuts the background to a transparent PNG, or swaps in a white, red or blue backdrop. - [Video Screenshot](https://qilingtools.com/en/video/screenshot): Free online video frame grabber: enter a timestamp and save that frame as a full-resolution PNG or JPG. Processed locally, no upload. - [QR Code Generator](https://qilingtools.com/en/qrcode): Free online QR code generator: turn URLs, text, Wi-Fi or contact cards into QR codes with custom size, colour and error correction. Crisp PNG or vector SVG. - [Rotate / Flip Image](https://qilingtools.com/en/image/rotate): Free online image rotate and flip tool: rotate JPG, PNG and WebP by 90, 180 or 270 degrees either way, flip horizontally or vertically, batch supported. - [Crop Image](https://qilingtools.com/en/image/crop): Free online image cropper: drag on the image to select any area and download the crop. Supports JPG/PNG/WebP, keeps the original format, processed locally. - [Adjust Image Colours](https://qilingtools.com/en/image/adjust): Free online image colour adjuster: tune brightness, contrast and saturation, or apply black & white, sepia, invert, warm and cool filters with a live preview. - [Blur / Pixelate Image](https://qilingtools.com/en/image/mosaic): Free online image redaction tool: drag to mark any area and hide it with pixelation, blur or a black box — several areas at once, for faces and plates. - [Round Image Corners](https://qilingtools.com/en/image/round-corner): Free online tool to round an image's corners or crop it into a circle avatar. Adjustable radius, transparent PNG output, batch supported. Runs locally. - [Add Border to Image](https://qilingtools.com/en/image/border): Free online tool to add a white or coloured border to photos, pad an image to a square for Instagram, or make a Polaroid-style frame. Batch supported. - [Split Image into Grid](https://qilingtools.com/en/image/grid): Free online image grid splitter: cut a picture into a 3×3 grid for Instagram, or 2×2, 1×3, 2×3 and more. Tiles are numbered in order and zipped. Runs locally. - [Remove EXIF Data](https://qilingtools.com/en/image/remove-exif): Free online EXIF viewer and remover: see the camera, capture time and GPS location hidden in a photo, then strip the metadata losslessly before sharing. - [Image Color Picker](https://qilingtools.com/en/image/color-picker): Free online image colour picker: click anywhere on an image to get its HEX, RGB and HSL values, and extract the dominant colour palette automatically. - [Image to Base64](https://qilingtools.com/en/image/base64): Free online image Base64 converter: turn an image into a Base64 string or Data URI with ready CSS and HTML snippets, or decode Base64 back to a file. - [Favicon Generator](https://qilingtools.com/en/image/favicon): Free online favicon generator: turn a PNG, JPG or SVG into a multi-size favicon.ico plus Apple Touch, Android and PWA icons, a webmanifest and the HTML tags. - [ID Photo Maker](https://qilingtools.com/en/image/id-photo): Free online ID and passport photo maker: AI replaces the background with white, blue or red, crops to passport, visa and 1-inch sizes at 300dpi, prints a sheet. - [Compress to Size](https://qilingtools.com/en/image/compress-to-size): Free online tool to compress an image to an exact file size: enter a target in KB and the photo is squeezed under it, keeping as much detail as it can. - [Remove White Background](https://qilingtools.com/en/image/remove-white): Free online tool to make a white or solid-colour background transparent with smooth, halo-free edges — ideal for signatures, stamps, logos and product shots. - [Photo Collage](https://qilingtools.com/en/image/collage): Free online collage maker: arrange several photos into one grid image with adjustable columns, cell shape, spacing and background. Drag to reorder. - [GIF Maker](https://qilingtools.com/en/image/to-gif): Free online GIF maker: turn a series of images into an animated GIF with adjustable frame time, size, looping and bounce playback. Drag to reorder. - [Split Long Image](https://qilingtools.com/en/image/split): Free online long image splitter: cut long screenshots and posters by piece count, fixed height or phone screen ratio, numbered in order and zipped. - [HEIC to JPG](https://qilingtools.com/en/image/heic-to-jpg): Free online HEIC to JPG converter: batch-convert iPhone HEIC / HEIF photos to JPG, PNG or WebP with correct orientation, so they open anywhere. Runs locally. - [SVG to PNG](https://qilingtools.com/en/image/svg-to-png): Free online SVG to PNG converter: export SVG vectors to crisp PNG, JPG or WebP at 1x–8x scale or any width, with a transparent or white background. Batch ready. - [Screenshot Beautifier](https://qilingtools.com/en/image/screenshot-beautify): Free online screenshot beautifier: add gradient backgrounds, padding, rounded corners, shadows and macOS or browser window frames. Runs locally, no upload. - [Photo to Sketch](https://qilingtools.com/en/image/sketch): Free online photo to sketch converter: turn photos into pencil sketches, clean line art or coloured-pencil drawings, with adjustable stroke width and depth. - [Sharpen Image](https://qilingtools.com/en/image/sharpen): Free online image sharpener: an unsharp mask brings back detail and edges in slightly blurry photos, with amount, radius and threshold and a 1:1 preview. - [Pixel Art Maker](https://qilingtools.com/en/image/pixel-art): Free online pixel art generator: turn photos into retro pixel art with adjustable pixel size and palettes, plus an optional grid for bead or cross-stitch. - [ASCII Art Generator](https://qilingtools.com/en/image/ascii-art): Free online ASCII art generator: convert images into text art with adjustable width and character sets, optional inversion, and copy or download as TXT or PNG. - [Add Text to Image](https://qilingtools.com/en/image/add-text): Free online tool to add text to images: drag text boxes anywhere, with size, colour, outline, shadow and several fonts, plus a classic top/bottom meme template. - [Blur Background](https://qilingtools.com/en/image/blur-background): Free online background blur: AI finds the person, pet or product and blurs only the background for a DSLR look, or leaves the subject alone in colour. - [Compare Images](https://qilingtools.com/en/image/compare): Free online image comparison tool: drag a divider between two images to check edits, compression or grading, and export side-by-side or split before/after. - [QR Code Scanner](https://qilingtools.com/en/image/qr-scan): Free online QR code scanner: upload or paste a screenshot to decode the QR codes inside, read the link or text and copy it. Batch supported, decoded locally. - [Change Image DPI](https://qilingtools.com/en/image/dpi): Free online DPI changer: set the resolution tag of a JPG or PNG to 300, 350, 72 or any value without touching the pixels, with the print size in millimetres. - [Image to Text (OCR)](https://qilingtools.com/en/image/ocr): Free online OCR: pull Chinese, English and numbers out of screenshots, photos and scans, then copy or download as TXT. The model runs in your browser. - [ID Card Copy](https://qilingtools.com/en/image/id-card-copy): Free online ID card copy maker: front and back laid out at the real 85.6×54mm on one A4 page, with an optional anti-misuse watermark. Export JPG or PDF. - [AI Image Upscaler](https://qilingtools.com/en/image/upscale): Free online AI image upscaler: enlarge photos and screenshots 2x or 4x with Real-ESRGAN, clearing blur and compression noise. The model runs in your browser. - [Document Scanner](https://qilingtools.com/en/image/scan): Free online document scanner: detect the page in a phone photo, straighten it with perspective correction, remove shadows, and export a scan, JPG or PDF. - [Remove Watermark / Object](https://qilingtools.com/en/image/remove-watermark): Free online watermark and object remover: paint over watermarks, date stamps or small objects and the area is filled in from the surrounding background. - [Replace Colour](https://qilingtools.com/en/image/replace-color): Free online colour replacer: click a colour in your image and swap it for another while keeping the shading and texture — for clothes, logos and products. - [Extract PDF Images](https://qilingtools.com/en/pdf/extract-images): Free online PDF image extractor: pull embedded pictures out at their original resolution as PNG or JPG, with fragment filtering and duplicate removal. - [Barcode Generator](https://qilingtools.com/en/barcode): Free online barcode generator: Code 128 with automatic code sets, EAN-13 with its check digit and Code 39. Adjust size, quiet zone and colours; SVG or PNG. - [PDF to Long Image](https://qilingtools.com/en/pdf/to-long-image): Free online PDF to long image converter: stack the pages you pick into one tall JPG or PNG, with adjustable width, gap and background. Huge results auto-split. - [Image Info Viewer](https://qilingtools.com/en/image/info): Free online image info and EXIF viewer: dimensions, file size, format, bit depth, DPI and ICC profile, plus camera, lens, exposure, date, GPS and a histogram. - [Image Color Palette](https://qilingtools.com/en/image/palette): Free online colour palette extractor: find the 3–16 dominant colours with percentages, copy HEX / RGB / HSL and export CSS variables, JSON or a PNG strip. - [Photo Print Layout](https://qilingtools.com/en/image/print-layout): Free online photo print layout: tile ID photos at 300 DPI onto 4×6, 5×7, A4 or Letter paper with gaps, cut lines and copies, then export JPG or PDF. - [Social Media Image Resizer](https://qilingtools.com/en/image/social-size): Free online social media image resizer: crop one image to 20 platform sizes — YouTube thumbnail, Instagram, X, Facebook, LinkedIn, TikTok — exported as a zip. - [Text to Image](https://qilingtools.com/en/image/text-to-image): Free online text to image tool: turn a quote or long post into a clean image with paper, dark, gradient, notebook and mint themes and smart line wrapping. - [Chart Maker](https://qilingtools.com/en/chart): Free online chart maker: paste data from Excel or CSV to build bar, line, area, pie, donut and scatter charts, then download a 2× PNG or an editable SVG. - [Video to Frames](https://qilingtools.com/en/video/to-frames): Free online video frame extractor: export every frame, every Nth frame or N frames per second as PNG or JPG, within a time range, all zipped up. - [App Icon Generator](https://qilingtools.com/en/image/app-icon): Free online app icon generator: turn one 1024px image into an iOS appiconset, Android mipmaps and adaptive icons, PWA icons, a Windows ICO and a macOS ICNS. - [GIF Editor](https://qilingtools.com/en/image/gif-edit): Free online GIF editor: delete, duplicate and reorder frames, change delays, reverse, boomerang, crop, resize and set the loop count, then re-export the GIF. - [Signature Maker](https://qilingtools.com/en/image/signature): Free online e-signature tool: photograph a handwritten signature for a clean transparent PNG with paper and shadows removed, or draw one and export PNG or SVG. - [CSS Sprite Generator](https://qilingtools.com/en/image/sprite): Free online CSS sprite generator: pack icons into one sheet with bin packing, grid or row layouts and @2x support, and get the CSS positions, or slice one. - [Photo Filters](https://qilingtools.com/en/image/filter): Free online photo filters: 13 looks — vintage film, black & white, noir, sepia, warm, cool, teal & orange, Lomo, faded — previewed on your photo, batch ready. - [Camera Info Frame](https://qilingtools.com/en/image/camera-frame): Free online camera watermark maker: reads brand, model, focal length, aperture, shutter, ISO and date from EXIF and adds an info bar or clean border. - [Image to SVG](https://qilingtools.com/en/image/to-svg): Free online image to SVG converter: trace PNG and JPG bitmaps into scalable vectors, with presets for line art, logos and photos and adjustable smoothing. - [Image Denoiser](https://qilingtools.com/en/image/denoise): Free online photo noise reduction: clear luminance grain and colour blotches from low-light shots with edge-preserving filtering, compare at 1:1, batch ready. - [Image Dithering](https://qilingtools.com/en/image/dither): Free online image dithering: turn photos into 1-bit black & white, 4-level grey, e-ink or Game Boy palettes with Floyd–Steinberg, Atkinson or Bayer ordering. - [Blur Faces](https://qilingtools.com/en/image/blur-faces): Free online face blurring: AI finds every face in a photo, including small ones in group shots, and pixelates, blurs, blacks out or covers them with an emoji. - [Auto Enhance Photo](https://qilingtools.com/en/image/auto-enhance): Free online one-click photo enhancer: auto white balance, auto levels, auto exposure and smart vibrance, each photo analysed on its own. Batch ready. - [Photo to Oil Painting](https://qilingtools.com/en/image/oil-paint): Free online photo to oil painting converter: a Kuwahara filter adds brush strokes, with adjustable brush size, colour richness and optional canvas texture. - [Tilt-Shift Effect](https://qilingtools.com/en/image/tilt-shift): Free online tilt-shift effect: blur the top and bottom while one band stays sharp, then boost colours, turning streets and crowds into toy-like miniatures. - [Image Steganography](https://qilingtools.com/en/image/steganography): Free online image steganography: hide a message in the least significant bits of a PNG, optionally AES-256 encrypted, and reveal hidden text again. - [Smart Crop](https://qilingtools.com/en/image/smart-crop): Free online smart crop: finds the subject and keeps faces in frame while batch-cropping to 1:1, 4:5, 3:4, 9:16, 16:9 or a custom ratio, with fixed output width. - [Duotone / Gradient Map](https://qilingtools.com/en/image/duotone): Free online duotone tool: map brightness to a gradient between two or three colours, with 10 ready-made schemes or your own shadow and highlight colours. - [Halftone Effect](https://qilingtools.com/en/image/halftone): Free online halftone generator: turn photos into dot patterns — one-colour dots, four-colour CMYK screens or a line screen — for comic and vintage print looks. - [Glitch Effect](https://qilingtools.com/en/image/glitch): Free online glitch art generator: add RGB split, tearing, corrupted blocks, noise and scanlines, each with its own strength, or randomise it in one click. - [Double Exposure](https://qilingtools.com/en/image/double-exposure): Free online double exposure maker: blend a portrait with a landscape or texture using screen, multiply, overlay or soft-light, with opacity, zoom and position. - [Sticker Outline](https://qilingtools.com/en/image/sticker): Free online sticker maker: add an even white outline and a soft drop shadow around a transparent PNG; photos get their background removed by AI first. - [Straighten Image](https://qilingtools.com/en/image/straighten): Free online image straightener: rotate by any angle to 0.1°, auto-detect tilted horizons, then crop the empty corners or fill them, with a guide grid. - [Mirror & Kaleidoscope](https://qilingtools.com/en/image/mirror): Free online mirror effect tool: flip and copy an image's left, right, top or bottom half for symmetry, go four-way, or make 4–24 segment kaleidoscope patterns. - [Photo Mosaic](https://qilingtools.com/en/image/photo-mosaic): Free online photo mosaic maker: rebuild a picture out of hundreds of small photos, matched by colour and spaced to avoid repeats, with adjustable grid size. - [Cross-Stitch Pattern Maker](https://qilingtools.com/en/image/cross-stitch): Free online cross-stitch pattern generator: turn photos into charts with coloured cells, symbols and numbering, a colour key with stitch counts and a preview. - [Curves Adjustment](https://qilingtools.com/en/image/curves): Free online curves tool: drag points on the RGB master curve and each channel over a live histogram, with presets for S-curve contrast, faded film and invert. - [Apply LUT (.cube)](https://qilingtools.com/en/image/lut): Free online LUT tool: load a .cube or Hald CLUT PNG and apply it to photos with trilinear interpolation, adjustable strength, live preview and batch processing. - [Color Blindness Simulator](https://qilingtools.com/en/image/color-blind): Free online colour blindness simulator: view images as protanopia, deuteranopia, tritanopia or achromatopsia, adjust severity and compare every type. - [Line Art Extractor](https://qilingtools.com/en/image/line-art): Free online line art extractor: turn photos and illustrations into clean black-and-white line drawings, with adjustable thickness, detail and speck cleanup. - [Jigsaw Puzzle Maker](https://qilingtools.com/en/image/jigsaw): Free online jigsaw puzzle maker: cut a photo into 12–1000 tabbed pieces and export a printable sheet with cut lines, an SVG cutting template or loose PNGs. - [Video Contact Sheet](https://qilingtools.com/en/video/contact-sheet): Free online video contact sheet maker: tile N×M evenly spaced frames into one image, each with a timestamp, under a header of file and stream details. - [Word Cloud Generator](https://qilingtools.com/en/word-cloud): Free word cloud maker: paste text or open a file, word counts with stopword removal, editable frequency table, heart, star or image shapes, PNG and SVG. - [Avatar Generator](https://qilingtools.com/en/image/avatar): Free avatar generator: initials colored by name (CJK aware), GitHub-style identicons and geometric avatars. Circle or square, batch ZIP, PNG/SVG. - [Wallpaper & Background Generator](https://qilingtools.com/en/image/background-generator): Free wallpaper generator: mesh and linear gradients, blobs, waves, low poly, hexagons, dots, stripes and grain. Palettes, 4K sizes, PNG/JPG/SVG. - [Photo to Cartoon](https://qilingtools.com/en/image/cartoon): Free photo to cartoon converter: smooth flat colors and bold outlines, with comic, anime and watercolor presets, live preview and batch export. - [Meme Generator](https://qilingtools.com/en/image/meme): Free meme maker for your own images: classic Impact top and bottom text, a modern caption bar, and draggable, rotatable text and emoji stickers. PNG/JPG. - [Screenshot Annotator](https://qilingtools.com/en/image/annotate): Free screenshot annotator: paste with Ctrl+V, add arrows, boxes, numbered steps, highlighter and text, pixelate or blur secrets, crop, copy or save PNG/JPG. - [EXIF Editor](https://qilingtools.com/en/image/exif-edit): Free EXIF editor: view all JPEG tags, change or bulk-shift the date taken, set or remove GPS, edit camera, artist and copyright, with no recompression. - [Placeholder Image Generator](https://qilingtools.com/en/image/placeholder): Free placeholder image generator: custom size, colors and text with auto-fit font, PNG, JPG, WebP or SVG, batch sizes to ZIP, or copy a data URI or SVG. - [Code Screenshot](https://qilingtools.com/en/code-screenshot): Turn code into beautiful images: auto-detected syntax highlighting, 10 themes, macOS window, line numbers, gradient backgrounds, PNG up to 4x or SVG. - [Video Thumbnail Maker](https://qilingtools.com/en/video/cover): Free video thumbnail maker: pick any frame or upload an image, add bold titles with outline, bars, emoji and gradients, sized for YouTube, TikTok and more. - [Color Transfer](https://qilingtools.com/en/image/color-transfer): Copy a reference photo’s color grade onto your images with Reinhard, histogram matching or MKL. Adjustable strength, batch mode and .cube LUT export. - [Panorama Stitcher](https://qilingtools.com/en/image/panorama): Stitch 2–10 overlapping photos into a panorama: automatic order and alignment, cylindrical projection, exposure compensation, seamless blending, auto-crop. - [QR Code Art Generator](https://qilingtools.com/en/qr-art): Free styled QR code maker for URLs, Wi-Fi, vCards, email, SMS and maps: dot or diamond modules, custom eyes, gradients, logo, PNG/SVG/JPG and a scan check. - [Text to Handwriting](https://qilingtools.com/en/image/handwriting): Free text to handwriting converter: natural size, tilt and ink variation on lined, grid, kraft or letter paper, auto pages, scan/photo look. PNG, ZIP, PDF. - [Portrait Retouch](https://qilingtools.com/en/image/retouch): Free portrait retouching: AI face detection, edge-preserving skin smoothing, brighten and even tone, teeth and eyes, click-to-heal blemishes, slim face. - [Text Behind Image](https://qilingtools.com/en/image/text-behind): Free text behind image maker: AI cuts out the subject so big text sits between background and person. Multiple layers, stroke, shadow, glow; full-res PNG/JPG. - [Duplicate Photo Finder](https://qilingtools.com/en/image/duplicates): Find duplicate and similar photos in your browser: SHA-256 for identical files, perceptual hashes for resized or recompressed copies; keep the best, export CSV. - [HDR Merge](https://qilingtools.com/en/image/hdr): Merge 2–7 bracketed exposures with MTB alignment, Mertens exposure fusion and ghost reduction — no camera response needed — or give one photo an HDR look. - [Film Negative Converter](https://qilingtools.com/en/image/negative): Convert scanned film negatives to positives online: orange mask removal, per-channel auto balance, white balance, tone curves, dust removal and batch export. - [Pixel Sorting](https://qilingtools.com/en/image/pixel-sort): Pixel sort images online: sort by brightness, hue or RGB within threshold, edge, random or brush-mask intervals at any angle, seeded, with full-res PNG export. - [Drawing Grid Maker](https://qilingtools.com/en/image/drawing-grid): Add an artist’s drawing grid to a photo: count or cm/in cells, diagonals, thirds, golden ratio, labels, value study, and print to scale across pages. - [Seamless Texture Maker](https://qilingtools.com/en/image/seamless): Make photos and textures tile seamlessly: mirror tiling, cross-fade edges or patch-based seam healing, offset and tiled previews, plus a repeat-pattern maker. - [Procedural Texture Generator](https://qilingtools.com/en/image/texture): Procedural textures online: Perlin/Simplex fBm, ridged, turbulence, Worley, domain warp, 10 presets, colour ramps, seamless tiling, 4096 PNG and normal maps. - [Social Feed Grid Planner](https://qilingtools.com/en/image/feed-planner): Plan your profile grid: reorder a 3-column feed, waterfall or 9-photo post, schedule dates and captions, check colour harmony, split puzzle grids and carousels. - [Device Mockup Generator](https://qilingtools.com/en/image/mockup): Put screenshots into phone, tablet, laptop, monitor, browser and watch frames online, with 3D perspective tilt, multi-device scenes and 4K PNG export. - [Sprite Sheet Animator](https://qilingtools.com/en/image/sprite-animate): Animate sprite sheets online: auto-detect the grid, set frame order, fps and onion skin, export GIF, APNG, WebP or frames — or pack frames into a sheet + JSON. - [Logo Maker](https://qilingtools.com/en/image/logo): Free logo maker: round badges with curved text, shield, hexagon and ribbon shapes, 68 line icons or emoji, monograms, palettes, SVG and transparent PNG. - [Poster Print (Rasterbator)](https://qilingtools.com/en/image/poster-print): Print one image across many A4 or Letter pages: page grid or width, overlaps, cut marks, A1/B2 labels, rasterbator-style halftone dots, PDF or print. - [Shape Photo Collage](https://qilingtools.com/en/image/shape-collage): Turn photos into a heart, star, letters, numbers or any silhouette: grid or packed circles, spacing, rotation, borders, seeded shuffle, PNG up to 4000 px. - [Batch Image Processing](https://qilingtools.com/en/image/batch): Free online batch image tool: run a whole folder of photos through resizing, a text watermark, JPG/PNG/WebP conversion and numbered renaming, download as ZIP. - [Seal Extractor](https://qilingtools.com/en/image/seal): Free online seal extractor: lift a red or blue stamp off a scan into a transparent PNG, dropping paper, tint and specks. Solid colour, auto-trim, runs locally. ### Audio Tools - [Convert Audio](https://qilingtools.com/en/audio/convert): Free online audio converter: convert between MP3, WAV, M4A, AAC, FLAC, OGG and OPUS with selectable bitrate. Powered by FFmpeg, processed locally, no upload. - [Trim Audio](https://qilingtools.com/en/audio/trim): Free online audio trimmer: set start and end times to cut a clip from MP3, WAV, M4A and more. Make ringtones. Processed locally, no upload. - [Merge Audio](https://qilingtools.com/en/audio/merge): Free online audio merger: join MP3, WAV and other audio files in order into one file, mixed formats supported. Processed locally, no upload. - [Volume / Speed](https://qilingtools.com/en/audio/volume): Free online audio volume booster: amplify or reduce volume and change playback speed (0.5x to 3x without pitch change). Processed locally, no upload. - [Audio Fade In/Out](https://qilingtools.com/en/audio/fade): Free online audio fade tool: add a fade-in at the start and a fade-out at the end of MP3, WAV and more, with any length. Batch supported, runs locally. - [Normalize Audio](https://qilingtools.com/en/audio/normalize): Free online loudness normalizer: bring a batch of files to the same perceived loudness with EBU R128 / LUFS, or even out uneven speech with compression. - [Split Audio](https://qilingtools.com/en/audio/split): Free online audio splitter: cut long recordings, album rips and audiobooks into parts by count, fixed length or specific time points, downloaded as a zip. - [Mix Audio](https://qilingtools.com/en/audio/mix): Free online audio mixer: play voice, a backing track and background music together, with adjustable levels and a built-in limiter. Processed locally. - [Change Audio Pitch](https://qilingtools.com/en/audio/pitch): Free online pitch shifter: move a song or recording up to 12 semitones up or down while keeping the tempo — for transposing backing tracks and voice changing. - [Reduce Audio Noise](https://qilingtools.com/en/audio/denoise): Free online audio denoiser: strip air-conditioning hum, hiss and fan noise from recordings, with adjustable strength and optional speech boost. No upload. - [Remove Silence](https://qilingtools.com/en/audio/silence): Free online silence remover: cut the dead air at the start and end of a recording and shorten long pauses in the middle, with an adjustable threshold. - [Audio Equalizer](https://qilingtools.com/en/audio/equalizer): Free online audio EQ: adjust bass, mid and treble gain separately, with bass boost, vocal, bright, warm and telephone presets and a built-in limiter. - [Extract Audio](https://qilingtools.com/en/video/extract-audio): Free online tool to extract audio from MP4, MOV and other videos as MP3, M4A or WAV. Processed locally, no upload. - [Mute Video](https://qilingtools.com/en/video/mute): Free online video muter: remove the audio track from a video in one click without re-encoding the picture. Finishes in seconds, processed locally, no upload. - [Replace Video Audio](https://qilingtools.com/en/video/audio-track): Free online tool to replace a video soundtrack or layer music over the original audio, with adjustable volume and looping. The picture is not re-encoded. - [Text to Speech](https://qilingtools.com/en/text-to-speech): Free text to speech: near-human AI voices run in your browser, unlimited, downloadable as WAV, in English and Chinese. System voices cover many more languages. - [Reverse Audio](https://qilingtools.com/en/audio/reverse): Free online audio reverser: play MP3, WAV, M4A and more backwards from end to start, with your choice of output format and bitrate. Batch supported, no upload. - [Audio to Video](https://qilingtools.com/en/audio/to-video): Free online audio to video converter: pair an MP3 or WAV with a cover image or solid background and a title, and export a 16:9, 1:1 or 9:16 MP4. Runs locally. - [Audio Waveform Generator](https://qilingtools.com/en/audio/waveform): Free online audio waveform generator: render MP3, WAV and more as bar, mirrored, line or filled sound-wave images with custom colors and sizes. PNG and SVG. - [Online Voice Recorder](https://qilingtools.com/en/audio/record): Free online voice recorder: record from your microphone with noise suppression, pause and resume, a live level meter and waveform, then save as MP3 or WAV. - [Audio Tag Editor](https://qilingtools.com/en/audio/tags): Free online audio tag editor: edit title, artist, album, year, genre and track number in MP3, M4A, FLAC, OGG and WAV, and replace the cover — no re-encoding. - [BPM Detector](https://qilingtools.com/en/audio/bpm): Free online BPM detector: find a song's tempo to 0.1 BPM with a confidence score and half/double-time candidates, see every beat on the waveform, or tap along. - [Online Metronome](https://qilingtools.com/en/audio/metronome): Free online metronome: 20–300 BPM with tap tempo, common and custom time signatures, accents, eighth, triplet and sixteenth subdivisions and three sounds. - [Tone Generator](https://qilingtools.com/en/audio/tone-generator): Free online tone generator: sine, square, sawtooth and triangle waves from 1 to 20,000 Hz, a note picker, sweeps, white/pink/brown noise and a WAV download. - [Vocal Remover](https://qilingtools.com/en/audio/vocal-remover): Free online vocal remover: center-channel cancellation turns a track into a karaoke instrumental, with a keep-the-bass option and approximate vocal extraction. - [Ringtone Maker](https://qilingtools.com/en/audio/ringtone): Free online ringtone maker: drag on the waveform to pick a section and export an iPhone .m4r (up to 40 s) or Android MP3 / OGG, with fades and normalization. - [Audio Spectrogram](https://qilingtools.com/en/audio/spectrogram): Free online spectrogram generator: see time, frequency and level from a Hann-windowed STFT, with FFT size, log axis, dB range and colour maps. Exports PNG. - [8D Audio Converter](https://qilingtools.com/en/audio/8d): Free 8D audio maker: make any song circle your head with adjustable speed, width and reverb. Preview 15 s, export MP3 or WAV. Best on headphones, runs locally. - [Audio Effects & Voice Changer](https://qilingtools.com/en/audio/effects): Free voice changer and audio effects: reverb, echo, chorus, flanger, robot, telephone, walkie-talkie, chipmunk, 8-bit and more. A/B preview, batch export. - [Speech to Text](https://qilingtools.com/en/speech-to-text): Free online speech to text: talk into your mic for live transcription in 20+ languages with timestamps, auto punctuation, editing and TXT or SRT export. - [White Noise & Ambient Sounds](https://qilingtools.com/en/audio/ambient): Free ambient sound mixer: white, pink and brown noise, rain, ocean, wind, fire, stream, birds, café and fan. Presets, sleep timer, saved mixes, MP3/WAV export. - [Online Piano](https://qilingtools.com/en/audio/piano): Free virtual piano: play with mouse, multi-touch or your computer keyboard, 2–4 octaves, piano, e-piano, organ and synth, sustain pedal, WAV/MIDI export, songs. - [Audio Channel Tools](https://qilingtools.com/en/audio/channels): Free audio channel tools: stereo to mono (mix or L/R), mono to stereo, swap or split channels, mute one side, balance, fix phase, 5.1 to stereo. - [Loudness Meter](https://qilingtools.com/en/audio/loudness): Free loudness meter: integrated LUFS, short-term/momentary max, LRA, true peak, RMS, DC offset and clipping, checked against Spotify, YouTube and EBU R128. - [Decibel Meter](https://qilingtools.com/en/audio/decibel): Free online decibel meter: measure noise with your mic in real time, A/C/Z weighting, fast/slow response, min/max/average/Leq, 60-second graph and calibration. - [Drum Machine](https://qilingtools.com/en/audio/drum-machine): Free online drum machine: 10 synthesized drums, 8/12/16/32-step grid, BPM, swing, accents, mute/solo, rock to bossa presets, export WAV and General MIDI. - [Online Tuner](https://qilingtools.com/en/audio/tuner): Free online tuner using your microphone: note, octave and cents in real time. Guitar standard, Drop D, Open G, DADGAD, bass, ukulele, violin, A4 415–466 Hz. - [PDF Read Aloud](https://qilingtools.com/en/pdf/read-aloud): Listen to a PDF read aloud sentence by sentence, highlighted in the text and on the page. Choose voices and speed, click to jump, and resume later. - [Audio Compressor & Limiter](https://qilingtools.com/en/audio/compressor): Free online audio compressor: threshold, ratio, knee, attack/release, auto makeup, true-peak limiter, noise gate, de-esser, presets and A/B preview. - [LRC Lyrics Maker](https://qilingtools.com/en/audio/lrc-maker): Free online LRC maker: tap Space to timestamp each line as the song plays, word-by-word enhanced LRC, draggable timeline, karaoke preview, LRC/SRT/VTT export. - [MIDI Player](https://qilingtools.com/en/audio/midi-player): Free online MIDI player: play .mid files with a live piano roll, mute or solo parts, change tempo, transpose, view track info and export WAV. - [Game Sound Effect Generator](https://qilingtools.com/en/audio/sfx): Free sfxr-style 8-bit sound effect generator: one-click coin, laser, explosion and jump sounds, tweak every parameter, export WAV and share by link. - [Jump Cut: Remove Video Pauses](https://qilingtools.com/en/video/jump-cut): Free automatic jump cut: detect pauses in talking-head or lecture videos, cut or speed them up with per-cut control, export MP4, EDL and CSV. - [Audio to MIDI](https://qilingtools.com/en/audio/to-midi): Turn humming, whistling, singing or a single instrument into MIDI online: pitch and onset detection, key snapping, quantize, editable piano roll, .mid export. - [Audiogram Maker](https://qilingtools.com/en/audio/audiogram): Turn podcast, interview or music clips into audiogram videos online: spectrum, waveform or circular visualizer, cover art, captions, progress bar, MP4 export. - [Chord & Scale Finder](https://qilingtools.com/en/audio/chords): Free chord library: every chord type in all 12 keys with guitar and ukulele voicings, piano view, a chord finder for inversions, and scale charts. - [Circle of Fifths](https://qilingtools.com/en/audio/circle-of-fifths): Interactive circle of fifths: key signatures, relative minors, diatonic chords with Roman numerals, playable progressions, transposer and capo tips. - [Seamless Loop Maker](https://qilingtools.com/en/audio/loop): Make seamless audio loops online: sample-accurate automatic loop points, zero-crossing snap, crossfades, preview, extend music, WAV with loop points or MP3. - [ABX Blind Listening Test](https://qilingtools.com/en/audio/abx): Free online ABX listening test: auto loudness matching and time alignment, seamless switching, loop regions, p-value verdict, blind AB preference, MP3 maker. - [DTMF Tones](https://qilingtools.com/en/audio/dtmf): Generate and decode phone keypad tones (DTMF, incl. A–D) online: keypad, WAV export, decode recordings or the mic with timestamps, and decode Morse from audio. ### Video Tools - [Compress Video](https://qilingtools.com/en/video/compress): Free online video compressor: shrink MP4, MOV and other formats with H.264 encoding and resolution scaling, at the strength you pick. Processed locally. - [Convert Video](https://qilingtools.com/en/video/convert): Free online video converter: convert MOV, MKV, AVI, FLV, WebM and more to MP4 or WebM. Powered by FFmpeg, processed locally, no upload. - [Trim Video](https://qilingtools.com/en/video/trim): Free online video trimmer: set start and end times to cut a clip; fast mode finishes in seconds without re-encoding. Processed locally, no upload. - [Video to GIF](https://qilingtools.com/en/video/to-gif): Free online video to GIF converter: cut a clip and create a high-quality animated GIF with adjustable frame rate and width. Processed locally, no upload. - [Extract Audio](https://qilingtools.com/en/video/extract-audio): Free online tool to extract audio from MP4, MOV and other videos as MP3, M4A or WAV. Processed locally, no upload. - [Video Screenshot](https://qilingtools.com/en/video/screenshot): Free online video frame grabber: enter a timestamp and save that frame as a full-resolution PNG or JPG. Processed locally, no upload. - [Mute Video](https://qilingtools.com/en/video/mute): Free online video muter: remove the audio track from a video in one click without re-encoding the picture. Finishes in seconds, processed locally, no upload. - [Merge Videos](https://qilingtools.com/en/video/merge): Free online video joiner: combine several MP4, MOV or MKV clips into one file, even when their resolution and frame rate differ. Processed locally. - [Change Video Speed](https://qilingtools.com/en/video/speed): Free online video speed changer: slow a clip to 0.25x or speed it up to 4x. The audio follows along with its pitch preserved. Processed locally, no upload. - [Watermark Video](https://qilingtools.com/en/video/watermark): Free online video watermarker: add a text watermark or a logo image with adjustable position, size, opacity, angle and full-frame tiling. Processed locally. - [Crop Video](https://qilingtools.com/en/video/crop): Free online video cropper: drag on the frame to select the area to keep, with 1:1, 9:16 and 16:9 presets to turn landscape footage into portrait. Runs locally. - [Rotate Video](https://qilingtools.com/en/video/rotate): Free online video rotator: turn sideways clips 90° or 180°, mirror them horizontally or flip them vertically. Batch supported, processed locally, no upload. - [Replace Video Audio](https://qilingtools.com/en/video/audio-track): Free online tool to replace a video soundtrack or layer music over the original audio, with adjustable volume and looping. The picture is not re-encoded. - [Burn Subtitles](https://qilingtools.com/en/video/subtitle): Free online subtitle burner: load an SRT or VTT file and hardcode the captions into the video, with adjustable size, colour and outline. No missing glyphs. - [Reverse Video](https://qilingtools.com/en/video/reverse): Free online video reverser: play a clip backwards with the audio reversed too, for rewind effects. Processed locally in your browser, no upload. - [GIF to Video](https://qilingtools.com/en/video/from-gif): Free online GIF to video converter: turn animated GIFs into MP4 or WebM at a fraction of the size, with repeat count and frame rate options. No upload. - [GIF Maker](https://qilingtools.com/en/image/to-gif): Free online GIF maker: turn a series of images into an animated GIF with adjustable frame time, size, looping and bounce playback. Drag to reorder. - [Audio to Video](https://qilingtools.com/en/audio/to-video): Free online audio to video converter: pair an MP3 or WAV with a cover image or solid background and a title, and export a 16:9, 1:1 or 9:16 MP4. Runs locally. - [Video Color Correction](https://qilingtools.com/en/video/adjust): Free online video colour tool: adjust brightness, contrast, saturation, gamma and hue, add sharpening or denoising, or apply black & white and sepia looks. - [Remove Video Watermark](https://qilingtools.com/en/video/delogo): Free online video watermark remover: box the logo or text and erase it with smart fill, blur or pixelation. Several areas at once, audio untouched. - [Video Fade In/Out](https://qilingtools.com/en/video/fade): Free online video fade tool: fade in at the start and out at the end, from and to black or white, with the audio fading in step. Batch supported. - [Loop Video](https://qilingtools.com/en/video/loop): Free online video looper: repeat a clip N times or stretch it to a set length, usually without re-encoding, and make forward-and-back boomerang loops too. - [Picture in Picture Video](https://qilingtools.com/en/video/picture-in-picture): Free online picture-in-picture maker: place another video or an image as an inset on your main video, with position, size and margin, and pick the audio mix. - [Resize Video](https://qilingtools.com/en/video/resize): Free online video resizer: change resolution to 1080p, 720p, 480p or a custom size, and convert to 9:16, 1:1 or 16:9 with blurred bars, colour bars or crop. - [Online Screen Recorder](https://qilingtools.com/en/video/screen-record): Free online screen recorder: capture a screen, window or tab with system and microphone audio, add a webcam bubble, then save as WebM or convert to MP4. - [Split Screen Video](https://qilingtools.com/en/video/stack): Free online split-screen video maker: place 2–4 videos side by side, stacked or in a 2×2 grid, with size and frame-rate matching, gap and audio mix. - [Video to Frames](https://qilingtools.com/en/video/to-frames): Free online video frame extractor: export every frame, every Nth frame or N frames per second as PNG or JPG, within a time range, all zipped up. - [Add Text to Video](https://qilingtools.com/en/video/add-text): Free online tool to add text to a video: several text layers, each with its own start and end time, dragged into place on a live preview, with fades. - [Compress Video to Size](https://qilingtools.com/en/video/compress-to-size): Free online video compressor with an exact size target: pick 8, 10, 25, 50 or 100 MB, get the bitrate from the duration and encode two-pass x264 to hit it. - [Video Contact Sheet](https://qilingtools.com/en/video/contact-sheet): Free online video contact sheet maker: tile N×M evenly spaced frames into one image, each with a timestamp, under a header of file and stream details. - [Video Info (MediaInfo Online)](https://qilingtools.com/en/video/info): Free MediaInfo-style video inspector: container, duration, bitrate, per-stream codec, resolution, frame rate, HDR hints, audio layout, subtitles and chapters. - [Photo Slideshow Maker](https://qilingtools.com/en/video/slideshow): Free online slideshow maker using your photos as they are: custom order and durations, 15 transitions, never-crop Ken Burns, music and per-image captions. - [Video Stabilizer](https://qilingtools.com/en/video/stabilize): Free online video stabilizer: removes hand-held shake and roll with smoothed camera paths, hardware-accelerated in your browser, with zoom-to-crop borders and a preview. - [Green Screen Remover](https://qilingtools.com/en/video/chroma-key): Free online chroma key: click to pick the key color, tune it live, then add a color, image or video background or export transparent WebM, ProRes MOV or PNG. - [Video Splitter](https://qilingtools.com/en/video/split): Free online video splitter: split into equal parts, every X seconds, by MB per part or at timeline markers. Fast lossless or frame-accurate mode, ZIP download. - [Video Frame Rate Converter](https://qilingtools.com/en/video/frame-rate): Free frame rate converter: convert video to 24, 25, 30, 50, 60 fps or any rate by dropping, blending or motion interpolation, plus smooth 2/4/8x slow motion. - [Apply LUT to Video](https://qilingtools.com/en/video/lut): Free video LUT tool: load .cube files (1D/3D) or use built-in looks like teal & orange, warm film, bleach bypass and B&W; adjust intensity, compare, export. - [Extract Subtitles from Video](https://qilingtools.com/en/video/extract-subtitles): Free subtitle extractor: list embedded tracks in MKV or MP4 with language, format and title, export SRT, WebVTT or ASS, batch to ZIP. No upload. - [Subtitle Editor](https://qilingtools.com/en/video/subtitle-editor): Free subtitle editor: open SRT, VTT, ASS, LRC, SBV or TXT, edit text and timing, shift, two-point sync, fix overlaps, find & replace and convert formats. - [Video Thumbnail Maker](https://qilingtools.com/en/video/cover): Free video thumbnail maker: pick any frame or upload an image, add bold titles with outline, bars, emoji and gradients, sized for YouTube, TikTok and more. - [Blur Faces in Video](https://qilingtools.com/en/video/blur-faces): Free online video face blur: AI detects and tracks every face to blur or pixelate it; keep chosen faces, add regions by hand, export MP4 with audio. - [Timelapse & Stop Motion Maker](https://qilingtools.com/en/video/timelapse): Free timelapse maker: speed up videos by factor or target length with deflicker and motion blur, or turn photos into stop motion with onion skin. MP4/GIF. - [Webcam Recorder](https://qilingtools.com/en/video/webcam-record): Free online webcam recorder: choose camera and mic, filters and skin smoothing, countdown, pause, snapshots and a teleprompter that isn’t recorded. WebM/MP4. - [Video Compare](https://qilingtools.com/en/video/compare): Compare two videos in sync: side by side, slider wipe, difference or flicker, frame stepping, per-frame PSNR / SSIM graphs and labeled MP4 export. - [Jump Cut: Remove Video Pauses](https://qilingtools.com/en/video/jump-cut): Free automatic jump cut: detect pauses in talking-head or lecture videos, cut or speed them up with per-cut control, export MP4, EDL and CSV. - [Video to Animated WebP](https://qilingtools.com/en/video/to-webp): Convert video to animated WebP or APNG online: trim, set frame rate, width, quality and loops, estimate size, preview and compare with GIF. - [Video Scene Detection](https://qilingtools.com/en/video/scene-detect): Detect shot and scene changes in a video online: adjustable threshold, scene thumbnails, contact sheet, CSV and EDL cut lists, YouTube chapters, scene clips. - [Text Video Maker](https://qilingtools.com/en/video/text-video): Make animated text and quote videos online: 9:16, 1:1, 16:9; typewriter, word pop, slide-up, zoom; gradient, image or video backgrounds; music; MP4 export. - [Audiogram Maker](https://qilingtools.com/en/audio/audiogram): Turn podcast, interview or music clips into audiogram videos online: spectrum, waveform or circular visualizer, cover art, captions, progress bar, MP4 export. - [Auto Reframe Video](https://qilingtools.com/en/video/reframe): Convert landscape video to vertical online: face tracking with smooth camera moves, manual keyframes, 9:16, 1:1 or 4:5, blurred background, MP4 with audio. - [Countdown Video Maker](https://qilingtools.com/en/video/countdown): Create countdown timer videos online: digital, flip clock, ring, big numbers or film leader, up to 60 minutes, with beeps, green screen or transparent WebM. - [Lyric Video Maker](https://qilingtools.com/en/video/lyrics): Make lyric and karaoke videos online: import LRC or SRT or tap-sync lyrics, word-by-word fill, scrolling lyrics, bouncing ball, cover art, MP4 with your song. - [Video Zoom & Pan](https://qilingtools.com/en/video/zoom): Add zoom and pan effects to video online: drag a box to set keyframes, eased transitions, punch-in, slow push-in and Ken Burns presets, 9:16 or 1:1, audio kept. - [Bilingual subtitles](https://qilingtools.com/en/video/subtitle-merge): Free bilingual subtitle merger: pair two SRT / VTT / ASS files by timing into one two-line subtitle, or split a bilingual file back into two. Runs in-browser. ### Math Tools - [Graphing Calculator](https://qilingtools.com/en/math/graph): Free online function graphing calculator: type sin(x), x^2 or 1/x and see the curve at once, with several functions, parametric and polar curves, PNG export. - [Scientific Calculator](https://qilingtools.com/en/math/calculator): Free online scientific calculator: type 2*(3+4)^2, sin(pi/6) or log(8,2) and see the answer as you type, with degrees or radians and a history list. - [Equation Solver](https://qilingtools.com/en/math/equation): Free online equation solver: enter coefficients for linear, quadratic (with discriminant, vertex and complex roots) and cubic equations, plus 2×2 systems. - [Fraction Calculator](https://qilingtools.com/en/math/fraction): Free online fraction calculator: add, subtract, multiply and divide fractions with automatic reduction, plus fraction ↔ decimal with repeating digits. - [Percentage Calculator](https://qilingtools.com/en/math/percentage): Free online percentage calculator: X% of Y, X as a percent of Y, increase and decrease, a value after a percentage change and the original behind it. - [Prime Factorization](https://qilingtools.com/en/math/prime): Free online prime factorization: factor an integer with exponents, list every divisor and their sum, test primality with neighbouring primes, or list a range. - [GCD and LCM](https://qilingtools.com/en/math/gcd-lcm): Free online GCD and LCM calculator: works with two or more integers, says whether they are coprime, shows each prime factorization and every Euclidean step. - [Statistics Calculator](https://qilingtools.com/en/math/statistics): Free online statistics calculator: paste a data set for the mean, median, mode, range, quartiles, variance, standard deviation, standard error and outliers. - [Combinations](https://qilingtools.com/en/math/combination): Free online combination and permutation calculator: exact C(n,r), P(n,r) and n! with big integers, plus repetition variants and the total number of subsets. - [Matrix Calculator](https://qilingtools.com/en/math/matrix): Free online matrix calculator: add, subtract and multiply matrices up to 8×8, transpose, and compute the determinant, inverse, matrix power and rank. - [Unit Converter](https://qilingtools.com/en/math/unit): Free online unit converter: length, area, volume, weight, temperature, time, speed, data, pressure, energy and angle — one value converts every unit at once. - [Random Numbers](https://qilingtools.com/en/math/random): Free online random number generator: integers or decimals in any range, with no-repeats and sorting, list shuffling and dice, from a cryptographic source. - [Roman Numerals](https://qilingtools.com/en/math/roman): Free online Roman numeral converter: a number to its Roman numeral or back, with validation of standard notation, a symbol-by-symbol breakdown and a table. - [Number to Words](https://qilingtools.com/en/math/number-words): Free online number to words converter: English words, English currency amounts, Chinese numerals and the financial uppercase form used on invoices. - [Geometry Calculator](https://qilingtools.com/en/math/geometry): Free online geometry calculator: area and perimeter of circles, triangles, polygons and more, plus volume and surface area of solids, with the formulas shown. - [Triangle Solver](https://qilingtools.com/en/math/triangle): Free online triangle solver: SSS, SAS, ASA, AAS and SSA inputs give every side and angle plus the area, perimeter, heights, circumradius and inradius. - [Sequence Calculator](https://qilingtools.com/en/math/sequence): Free online sequence calculator: nth term, sum of n terms, mean and infinite sum for arithmetic and geometric sequences, plus exact big-integer Fibonacci. - [Ratio Calculator](https://qilingtools.com/en/math/ratio): Free online ratio calculator: solve a:b = c:x, reduce decimal ratios to whole numbers, divide a total in a given ratio, and scale sizes by ratio. - [Complex Numbers](https://qilingtools.com/en/math/complex): Free online complex number calculator: arithmetic on a+bi, powers and nth roots by De Moivre, with modulus, argument, conjugate and polar form for each result. - [Scientific Notation](https://qilingtools.com/en/math/scientific-notation): Free online scientific notation converter: switch between plain numbers and a×10ⁿ, accept 3.5e6, and get engineering notation with SI prefixes and rounding. - [Derivative & Integral](https://qilingtools.com/en/math/calculus): Free online calculus calculator: first and second derivative at a point with the tangent line, or a definite integral by adaptive Simpson with an error bound. - [Probability Distributions](https://qilingtools.com/en/math/probability): Free online probability calculator: z-scores and cumulative normal probabilities, P(X=k) and P(X≤k) for binomial and Poisson, plus the mean and variance. - [Trigonometry](https://qilingtools.com/en/math/trigonometry): Free online trigonometry calculator: sin, cos, tan, cot, sec and csc from degrees or radians, inverse functions, DMS conversion and a special-angle table. - [Average Calculator](https://qilingtools.com/en/math/average): Free online average calculator: arithmetic mean, median, mode, geometric and harmonic mean and RMS in one pass, plus weighted averages for grades and GPAs. - [Interest Calculator](https://qilingtools.com/en/math/interest): Free online interest calculator: compound interest at any frequency with the effective annual rate, simple interest, monthly savings growth and loan payments. - [Coordinate Geometry](https://qilingtools.com/en/math/coordinate): Free online coordinate geometry calculator: distance, midpoint, slope, line equations, point-to-line distance with the foot, triangle centres and polar form. - [Vector Calculator](https://qilingtools.com/en/math/vector): Free online vector calculator for 2D and 3D: addition, scalar multiples, dot and cross products, magnitude, angle, unit vector and projections, with checks. - [Polynomial Calculator](https://qilingtools.com/en/math/polynomial): Free online polynomial calculator: type x^3-2x^2-5x+6 for all real and complex roots, factoring, the derivative and antiderivative, plus long division. - [Set Operations](https://qilingtools.com/en/math/set): Free online set calculator: union, intersection, differences and symmetric difference of two groups, with subset and disjoint checks and Jaccard similarity. - [Inequality Solver](https://qilingtools.com/en/math/inequality): Free online inequality solver: linear, quadratic and absolute-value inequalities with the answer in set and interval notation, a number line and the reasoning. - [System of Equations](https://qilingtools.com/en/math/linear-system): Free online linear system calculator: fill in the augmented matrix for 2 to 6 unknowns and get the RREF, ranks and the unique, empty or general solution. - [Linear Regression](https://qilingtools.com/en/math/regression): Free online linear regression and curve fitting: paste x and y columns for the least-squares line, r, R², residuals, predictions and quadratic or cubic fits. - [Logarithm Calculator](https://qilingtools.com/en/math/logarithm): Free online logarithm calculator: log_b(x) for any base with ln, lg and log₂ alongside and the change-of-base working, plus b^x and exponential equations. - [GPA Calculator](https://qilingtools.com/en/math/gpa): Free online GPA calculator: enter credits and grades for a GPA on the 4.0 scale, US letters, WES bands or a 5-point scale, with a target GPA planner. - [Significant Figures Calculator](https://qilingtools.com/en/math/significant-figures): Free online sig fig calculator: count significant figures digit by digit, round to N sig figs or decimals with six rounding modes, and compute by sig fig rules. - [Sudoku Solver](https://qilingtools.com/en/math/sudoku): Free online sudoku solver and generator: solve any 9×9 grid in milliseconds, flag invalid or multi-solution puzzles, get single-based hints and candidates. - [Truth Table Generator](https://qilingtools.com/en/math/truth-table): Free online truth table generator: enter a Boolean or propositional expression for the full table, tautology check, canonical DNF/CNF and Quine–McCluskey. - [Conic Sections](https://qilingtools.com/en/math/conic): Free online conic section calculator: from Ax²+Bxy+Cy²+Dx+Ey+F=0 identify the curve and get the standard form, centre, foci, eccentricity and asymptotes. - [Number Theory](https://qilingtools.com/en/math/number-theory): Free online number theory tools: modular exponentiation, modular inverses and Bézout coefficients, the Chinese remainder theorem and Euler's totient φ(n). - [China Income Tax Calculator (IIT)](https://qilingtools.com/en/math/income-tax): Free China individual income tax calculator: monthly gross to take-home with social insurance, 2023 deductions, cumulative withholding and annual bonus options. - [Long Division Calculator](https://qilingtools.com/en/math/long-division): Free long division calculator that shows the work: the bracket layout with every divide–multiply–subtract step, remainders, decimals and repeating bars. - [Mortgage Calculator](https://qilingtools.com/en/math/mortgage): Free mortgage calculator: monthly payment, fixed-payment vs equal-principal, total interest, taxes and insurance, extra payments and a yearly schedule as CSV. - [Math Worksheet Generator](https://qilingtools.com/en/math/worksheet): Free printable math worksheet generator for kids: addition and subtraction within 10 to 1000, times tables, division and mixed operations, with an answer key. - [3D Surface Plotter](https://qilingtools.com/en/math/3d-graph): Free online 3D surface plotter: type z = f(x, y) and drag to rotate a height-coloured surface — solid, wireframe or contour, several at once, with PNG export. - [Probability Simulator](https://qilingtools.com/en/math/dice): Free online probability simulator: coin flips, d4-d20 dice, weighted spinners and urn draws over a million trials, with live histograms and a chi-square test. - [Geometry Sketchpad](https://qilingtools.com/en/math/geometry-board): Free online geometry sketchpad: construct points, lines, circles and polygons, drag a free point and watch dependents update, with automatic measurements. - [Taylor Series](https://qilingtools.com/en/math/taylor): Free online Taylor series calculator: exact coefficients for f(x) at centre a up to order 20, as fractions, with truncation error and a plot against f. - [Confidence Intervals & Tests](https://qilingtools.com/en/math/hypothesis-test): Free online statistical inference: confidence intervals for means and proportions, one- and two-sample tests with the statistic, df, p-value and decision. - [Eigenvalues](https://qilingtools.com/en/math/eigenvalue): Free online eigenvalue calculator: 2×2 and 3×3 matrices — characteristic polynomial, eigenvalues (complex too), eigenvectors, trace and diagonalizability. - [Bayes’ Theorem](https://qilingtools.com/en/math/bayes): Free online Bayes calculator: enter a prior and likelihood (or prevalence, sensitivity, specificity) for the posterior, PPV, NPV and a natural frequency table. - [Pascal’s Triangle](https://qilingtools.com/en/math/pascal): Free online Pascal's triangle tool: generate any number of rows, highlight one for the full (a+b)ⁿ expansion and row sum, and look up any C(n, k) exactly. - [Discount Calculator](https://qilingtools.com/en/math/discount): Free discount calculator: sale price after % off and stacked discounts, spend-and-save deals, deal and unit price comparison, margin, markup, sales tax, tips. - [Limit Calculator](https://qilingtools.com/en/math/limit): Free limit calculator: lim x→a and x→±∞, left- and right-hand limits, 0/0, ∞/∞ and 1^∞ forms by series expansion; spots limits that do not exist. - [Matrix Step-by-Step](https://qilingtools.com/en/math/matrix-steps): Step-by-step matrix calculator: Gauss-Jordan elimination to RREF showing every row operation, plus determinant, inverse, rank and Ax = b in exact fractions. - [Time Calculator](https://qilingtools.com/en/math/time-calc): Free time calculator: add or subtract hours, minutes and seconds, time between two clock times (even overnight), timesheet totals and decimal hours. - [Angle Converter & Unit Circle](https://qilingtools.com/en/math/angle): Convert degrees ↔ radians (exact, as π/6 or 3π/4) ↔ DMS ↔ gradians ↔ turns, find coterminal and reference angles, and drag an interactive unit circle. - [Function Analyzer](https://qilingtools.com/en/math/function-analysis): Analyze f(x): domain, range, even/odd, period, zeros, monotonic intervals, extrema, concavity, inflection points and asymptotes, with a sign chart and graph. - [Mental Math Practice](https://qilingtools.com/en/math/mental-math): Timed math facts drills for kids: +, −, × and ÷ in 60-second sprint, 20-question or endless mode, with instant feedback, mistake review and personal bests. - [Multiplication Table](https://qilingtools.com/en/math/times-table): Interactive multiplication chart up to 12×12 or 20×20 with row and column highlighting, hide-the-answers practice, a times tables quiz, printing and PNG export. - [Big Number Calculator](https://qilingtools.com/en/math/big-number): Arbitrary-precision calculator: exact + − × ÷, 2^1000, 1000!, n choose k, Fibonacci, modular power, GCD/LCM, integer roots, primality and base conversion. - [Decimal to Fraction Converter](https://qilingtools.com/en/math/decimal-fraction): Convert terminating and repeating decimals (0.1(6), 0.[142857], 0.1666…) to fractions with steps, and fractions or percents to decimals with the repetend shown. - [Radical Simplifier & Calculator](https://qilingtools.com/en/math/radical): Simplify square, cube and nth roots (√72 = 6√2, ∛54 = 3∛2) with steps, rationalize denominators, add and multiply radicals, and get roots to 1000 digits. - [Scale Calculator](https://qilingtools.com/en/math/scale): Map distance ↔ real distance for any scale, find the scale from two lengths, 1:24, 1:64 and HO 1:87 model sizes, drawing scales, print DPI and area scale. - [Bézier Curve Editor](https://qilingtools.com/en/math/bezier): Free online Bézier curve tool: pen out anchors and handles to join degree 3, 4 or 5 segments into any shape, morph between shapes, export SVG or PNG. - [LaTeX Equation Editor](https://qilingtools.com/en/math/latex): Free online LaTeX equation editor with live preview, a symbol palette and common formulas. Export transparent PNG or SVG, or copy MathML to paste into Word. - [Derivative Calculator](https://qilingtools.com/en/math/derivative): Symbolic derivative calculator with steps: product, quotient, chain and power rules, log differentiation, higher-order and partial derivatives, point values. - [Box Plot Maker](https://qilingtools.com/en/math/box-plot): Box and whisker plots from pasted columns: Tukey, TI-84, Excel INC/EXC or Minitab quartiles, 1.5×IQR and 3×IQR outliers, mean, notches, PNG/SVG export. - [Graph Theory Algorithm Visualizer](https://qilingtools.com/en/math/graph-theory): Draw a graph, step through BFS, DFS, Dijkstra, Bellman-Ford, Floyd–Warshall, Prim, Kruskal, topological sort, SCCs, bipartite check, Euler paths and max flow. - [Linear Programming Solver](https://qilingtools.com/en/math/linear-programming): Solve linear programs typed naturally: every simplex tableau with the pivot (two-phase or Big M), graphical method, integer programs and shadow prices. - [Standard Normal Table (Z Table)](https://qilingtools.com/en/math/normal-table): Interactive z table with left, right, mean-to-z and central areas, shaded charts and inverse lookup, plus t, chi-square and F critical value tables. - [China Salary Calculator (Take-Home Pay)](https://qilingtools.com/en/math/salary): China take-home pay calculator: editable city social insurance and housing fund rates, special deductions, monthly IIT, bonus tax, employer cost, net-to-gross. - [Fourier Series & FFT Visualizer](https://qilingtools.com/en/math/fourier): Fourier series coefficients and animated partial sums for square, sawtooth, triangle or any function (Gibbs), draw-your-own epicycles and FFT spectra. - [Integral Calculator (Step by Step)](https://qilingtools.com/en/math/integral): Step-by-step integral calculator: substitution, by parts, partial fractions, trig powers, completing the square. Every answer is checked by differentiation. - [IRR & NPV Calculator](https://qilingtools.com/en/math/irr-npv): Investment calculator: NPV, IRR (detects multiple IRRs), MIRR, XNPV/XIRR on real dates, payback, discounted payback and PI. Matches Excel. - [Differential Equation Solver](https://qilingtools.com/en/math/ode): ODE tool: slope fields with click-to-trace solutions (RK4/RK45), Euler vs RK4 errors, phase portraits with equilibrium types, and 2nd-order linear ODEs. - [Sample Size & Power Calculator](https://qilingtools.com/en/math/sample-size): Sample size and power: survey proportions and means, two proportions, two-sample and paired t-tests (matches G*Power), A/B test size and duration. - [Classical Cipher Lab](https://qilingtools.com/en/math/cipher): Encode and decode Caesar/ROT13, Vigenère (with Kasiski auto-crack), Playfair, rail fence, affine, Bacon and substitution ciphers, plus an Enigma I simulator. - [Fractal Explorer](https://qilingtools.com/en/math/fractal): Zoom into the Mandelbrot set, Julia sets, Burning Ship, Tricorn and Newton fractals with multithreaded rendering, plus L-systems and the Barnsley fern. - [Game Theory Calculator](https://qilingtools.com/en/math/game-theory): Enter a two-player payoff matrix to find pure and mixed Nash equilibria with exact fractions, eliminate dominated strategies and solve zero-sum games. - [Markov Chain Calculator](https://qilingtools.com/en/math/markov): Enter a transition matrix with exact fractions to get the state diagram, n-step matrix Pⁿ, stationary distribution, classification and absorbing-chain results. - [24 Game](https://qilingtools.com/en/math/24): Play the 24 game online with timer, hints and scoring, or solve any 3–6 numbers for 24 (or any target) and see every distinct solution with duplicates removed. - [Online Abacus](https://qilingtools.com/en/math/abacus): Free online abacus: soroban (1/4) or suanpan (2/5). Move beads, set any number, watch step-by-step addition and subtraction, and practise flash anzan. - [Learn to Tell Time](https://qilingtools.com/en/math/clock): Interactive teaching clock: drag linked hands, see the time in words (quarter past three), work out elapsed time, take quizzes and print clock worksheets. - [Fraction Visualizer](https://qilingtools.com/en/math/fraction-visual): See fractions as pies, bars and number lines: equivalent fractions, comparing, adding unlike fractions, mixed numbers, simplifying and printable worksheets. - [Ksp Calculator](https://qilingtools.com/en/math/ksp): Free solubility product calculator with 80 Ksp values at 25 °C: Ksp to molar solubility, the common-ion effect, Q vs Ksp precipitation and hydroxide pH. - [Colligative Properties Calculator](https://qilingtools.com/en/math/colligative): Free colligative properties calculator: freezing point depression, boiling point elevation, osmotic pressure and Raoult's law, with Kf/Kb and molar mass. - [Chemical Kinetics Calculator](https://qilingtools.com/en/math/kinetics): Free chemical kinetics calculator: reaction orders and k with units by initial rates, zero, first and second-order rate laws, and Ea from the Arrhenius plot. - [Calorimetry & Specific Heat Calculator](https://qilingtools.com/en/math/calorimetry): Free calorimetry calculator: solve q = mcΔT with a specific heat table, find the final temperature of mixtures, get ΔH from coffee-cup and bomb calorimetry. - [SMILES Molecule Viewer](https://qilingtools.com/en/math/smiles): Free online SMILES viewer: draw a 2D skeletal structure and get the formula, molar and exact mass, unsaturation, rings, H-bond counts and a Lipinski check. - [Isotope Pattern Calculator](https://qilingtools.com/en/math/isotope-pattern): Free isotope pattern calculator: enter a formula, pick M, [M+H]+, [M+Na]+ or [M−H]− and get monoisotopic m/z, average mass and the isotope distribution. - [Unit Cells & Crystal Structures](https://qilingtools.com/en/math/crystal): Interactive 3D unit cells (SC, BCC, FCC, HCP, NaCl, CsCl, ZnS, diamond, perovskite) with atoms per cell, coordination number, packing efficiency and density. - [Light Energy & Atomic Spectra](https://qilingtools.com/en/math/spectroscopy): Convert wavelength, frequency and photon energy (eV, J, kJ/mol), compute hydrogen spectral lines, photoelectric stopping potential and de Broglie wavelength. - [Beer–Lambert & Calibration Curve](https://qilingtools.com/en/math/beer-lambert): Free Beer-Lambert calculator: solve A = εbc for any variable, convert absorbance and %T, and fit a calibration curve with R², unknowns, 95% CI and LOD/LOQ. - [Ionic Compound Formula & Naming](https://qilingtools.com/en/math/ionic-compound): Write ionic formulas from cation and anion by criss-cross, name compounds from formulas and find formulas from names, with acids, hydrates and a quiz. - [IUPAC Name Generator](https://qilingtools.com/en/math/organic-name): Name organic compounds from SMILES: IUPAC 2013 and traditional names, highlighted parent chain and step-by-step reasoning. Also name-to-structure and a quiz. - [Isomer Generator](https://qilingtools.com/en/math/isomers): List every structural isomer of a formula like C5H12, C4H10O or C3H6Cl2, with drawings, IUPAC names, SMILES, class counts and stereoisomer totals. - [Molecular Orbital Diagram](https://qilingtools.com/en/math/mo-diagram): MO diagrams for H₂–Ne₂, O₂²⁻, N₂⁺, CO, NO, CN⁻ and HF with Hund’s-rule filling: MO configuration, bond order, unpaired electrons, magnetism and HOMO/LUMO. - [Born–Haber Cycle Calculator](https://qilingtools.com/en/math/born-haber): Born–Haber cycle for NaCl, MgO, CaF₂, Al₂O₃ and more: built-in data, lattice energy or any unknown via Hess’s law, a scaled diagram and Kapustinskii comparison. - [Net Ionic Equation Calculator](https://qilingtools.com/en/math/net-ionic): Free net ionic equation calculator: it balances the equation, splits strong electrolytes by solubility rules, cancels spectator ions and checks the charge. - [IR Spectroscopy Table](https://qilingtools.com/en/math/ir-table): Free interactive IR correlation table: 60+ functional group bands with range, intensity and shape on a 4000–400 cm⁻¹ chart; enter peaks to identify groups. - [¹H NMR Spectrum Simulator](https://qilingtools.com/en/math/nmr): Simulate ¹H NMR spectra at 60–600 MHz from shifts, integrals and J values: splitting trees, multiplicity (t, q, dd, dt), journal peak lists and a shift table. - [Peptide & Protein Calculator](https://qilingtools.com/en/math/peptide): Peptide calculator: formula, monoisotopic and average mass, pI with charge vs pH curve, extinction coefficient, GRAVY, ESI m/z and DNA-to-protein translation. - [Central Limit Theorem Simulator](https://qilingtools.com/en/math/clt): Probability simulations: an animated Galton board vs binomial and normal curves, the central limit theorem, law of large numbers and Monte Carlo π. - [Complex Function Plotter (Domain Coloring)](https://qilingtools.com/en/math/domain-coloring): Plot complex functions f(z) by domain coloring: argument as hue, modulus contours, zeros, poles and singularities, with a Riemann sphere view and zoom. - [Linear Transformation Visualizer](https://qilingtools.com/en/math/linear-transform): Enter a 2×2 or 3×3 matrix and watch the grid rotate, scale, shear, reflect or project, with basis vectors, determinant, eigenvectors, inverse and composition. - [Polyhedra Viewer](https://qilingtools.com/en/math/polyhedra): Rotate the 5 Platonic and 13 Archimedean solids, prisms and pyramids in 3D: truncation, duals, Euler’s formula, area and volume, unfolding and printable nets. - [Chi-Square & ANOVA Calculator](https://qilingtools.com/en/math/anova): Chi-square goodness of fit and independence (Yates, Fisher exact, Cramér’s V), one-way and two-way ANOVA, Tukey HSD, Kruskal–Wallis and Levene’s test. - [Matrix Decomposition Calculator](https://qilingtools.com/en/math/decomposition): Step-by-step LU with pivoting in exact fractions, Cholesky, QR (Gram–Schmidt or Householder) and SVD with rank, condition number and low-rank approximation. - [FIRE Calculator](https://qilingtools.com/en/math/fire): Find your FIRE number and years to financial independence from income, spending and real returns, with Monte Carlo success rates, Coast FI and Barista FI. ### Chemistry Tools - [Significant Figures Calculator](https://qilingtools.com/en/math/significant-figures): Free online sig fig calculator: count significant figures digit by digit, round to N sig figs or decimals with six rounding modes, and compute by sig fig rules. - [Chemical Equation Balancer](https://qilingtools.com/en/chemistry/chemical-equation): Balance chemical equations by the algebraic method: smallest whole-number coefficients, brackets, hydrates, ionic charges, electrons, atom and charge checks. - [Molar Mass Calculator](https://qilingtools.com/en/chemistry/molar-mass): Molar mass of any formula with IUPAC atomic weights: brackets and hydrates, mass percent of each element, grams ↔ moles ↔ particles and solution molarity. - [Interactive Periodic Table](https://qilingtools.com/en/chemistry/periodic-table): Interactive periodic table of all 118 elements: colour by category, block, electronegativity, atomic mass, phase or melting point; search and click for details. - [pH Calculator](https://qilingtools.com/en/chemistry/ph): Free pH calculator for strong and weak acids and bases, polyprotic acids, salts and buffers, with an exact charge-balance solution and species plots. - [Titration Curve](https://qilingtools.com/en/chemistry/titration): Free acid-base titration curve simulator: exact curves for strong, weak and polyprotic acids and bases, equivalence-point pH, the jump and indicator picks. - [Gas Law Calculator](https://qilingtools.com/en/chemistry/gas-law): Free gas law calculator: solve PV=nRT for any variable, combined gas laws, gas density, Dalton's partial pressures, gas over water and van der Waals Z. - [Solution & Dilution Calculator](https://qilingtools.com/en/chemistry/solution): Free dilution calculator: solve C1V1=C2V2, convert molarity, % w/w, ppm and molality, mix solutions, plan serial dilutions and dilute stock acids. - [Stoichiometry & Limiting Reagent](https://qilingtools.com/en/chemistry/stoichiometry): Balances the equation, finds the limiting reactant from grams, moles, gas volume or molarity, and gives theoretical yield, excess and percent yield with steps. - [Empirical & Molecular Formula](https://qilingtools.com/en/chemistry/empirical-formula): Find the empirical and molecular formula from mass percent, element masses or combustion data (CO₂, H₂O, N₂), with a whole-number ratio search and full working. - [Electron Configuration Calculator](https://qilingtools.com/en/chemistry/electron-config): Free electron configuration calculator for any element or ion (Fe3+, O2-): full and noble-gas notation, an orbital diagram, unpaired electrons and shells. - [VSEPR Molecular Geometry](https://qilingtools.com/en/chemistry/vsepr): Free VSEPR calculator: enter SF4, NH4+ or SO4^2- for the steric number, lone pairs, AXE notation, electron and molecular geometry, angles and hybridization. - [Reaction enthalpy & Gibbs energy](https://qilingtools.com/en/chemistry/thermochem): Free ΔH, ΔS and ΔG calculator: type an equation, it balances it and looks up enthalpies of formation, then gives K, crossover temperature and spontaneity. - [Chemical equilibrium (ICE)](https://qilingtools.com/en/chemistry/equilibrium): Free equilibrium calculator: enter a reaction, K and initial concentrations for the ICE table, exact concentrations, Q vs K and the 5% rule check. - [Cell Potential & Nernst Calculator](https://qilingtools.com/en/chemistry/electrochem): Standard reduction potential table with cell reaction, notation, E°cell, ΔG° and K, plus Nernst equation, concentration cells and Faraday electrolysis. - [Oxidation Number Calculator](https://qilingtools.com/en/chemistry/oxidation-number): Oxidation numbers for any formula or ion with step-by-step rules, plus redox equation analysis: oxidizing and reducing agents and electrons transferred. - [Half-Life Calculator](https://qilingtools.com/en/chemistry/half-life): Solve radioactive decay for any unknown with 30+ isotopes: decay constant, activity in Bq and Ci, carbon-14 dating and first-order kinetics. - [Ksp Calculator](https://qilingtools.com/en/math/ksp): Free solubility product calculator with 80 Ksp values at 25 °C: Ksp to molar solubility, the common-ion effect, Q vs Ksp precipitation and hydroxide pH. - [Colligative Properties Calculator](https://qilingtools.com/en/math/colligative): Free colligative properties calculator: freezing point depression, boiling point elevation, osmotic pressure and Raoult's law, with Kf/Kb and molar mass. - [Chemical Kinetics Calculator](https://qilingtools.com/en/math/kinetics): Free chemical kinetics calculator: reaction orders and k with units by initial rates, zero, first and second-order rate laws, and Ea from the Arrhenius plot. - [Calorimetry & Specific Heat Calculator](https://qilingtools.com/en/math/calorimetry): Free calorimetry calculator: solve q = mcΔT with a specific heat table, find the final temperature of mixtures, get ΔH from coffee-cup and bomb calorimetry. - [SMILES Molecule Viewer](https://qilingtools.com/en/math/smiles): Free online SMILES viewer: draw a 2D skeletal structure and get the formula, molar and exact mass, unsaturation, rings, H-bond counts and a Lipinski check. - [Isotope Pattern Calculator](https://qilingtools.com/en/math/isotope-pattern): Free isotope pattern calculator: enter a formula, pick M, [M+H]+, [M+Na]+ or [M−H]− and get monoisotopic m/z, average mass and the isotope distribution. - [Unit Cells & Crystal Structures](https://qilingtools.com/en/math/crystal): Interactive 3D unit cells (SC, BCC, FCC, HCP, NaCl, CsCl, ZnS, diamond, perovskite) with atoms per cell, coordination number, packing efficiency and density. - [Light Energy & Atomic Spectra](https://qilingtools.com/en/math/spectroscopy): Convert wavelength, frequency and photon energy (eV, J, kJ/mol), compute hydrogen spectral lines, photoelectric stopping potential and de Broglie wavelength. - [Beer–Lambert & Calibration Curve](https://qilingtools.com/en/math/beer-lambert): Free Beer-Lambert calculator: solve A = εbc for any variable, convert absorbance and %T, and fit a calibration curve with R², unknowns, 95% CI and LOD/LOQ. - [Ionic Compound Formula & Naming](https://qilingtools.com/en/math/ionic-compound): Write ionic formulas from cation and anion by criss-cross, name compounds from formulas and find formulas from names, with acids, hydrates and a quiz. - [IUPAC Name Generator](https://qilingtools.com/en/math/organic-name): Name organic compounds from SMILES: IUPAC 2013 and traditional names, highlighted parent chain and step-by-step reasoning. Also name-to-structure and a quiz. - [Isomer Generator](https://qilingtools.com/en/math/isomers): List every structural isomer of a formula like C5H12, C4H10O or C3H6Cl2, with drawings, IUPAC names, SMILES, class counts and stereoisomer totals. - [Molecular Orbital Diagram](https://qilingtools.com/en/math/mo-diagram): MO diagrams for H₂–Ne₂, O₂²⁻, N₂⁺, CO, NO, CN⁻ and HF with Hund’s-rule filling: MO configuration, bond order, unpaired electrons, magnetism and HOMO/LUMO. - [Born–Haber Cycle Calculator](https://qilingtools.com/en/math/born-haber): Born–Haber cycle for NaCl, MgO, CaF₂, Al₂O₃ and more: built-in data, lattice energy or any unknown via Hess’s law, a scaled diagram and Kapustinskii comparison. - [Net Ionic Equation Calculator](https://qilingtools.com/en/math/net-ionic): Free net ionic equation calculator: it balances the equation, splits strong electrolytes by solubility rules, cancels spectator ions and checks the charge. - [IR Spectroscopy Table](https://qilingtools.com/en/math/ir-table): Free interactive IR correlation table: 60+ functional group bands with range, intensity and shape on a 4000–400 cm⁻¹ chart; enter peaks to identify groups. - [¹H NMR Spectrum Simulator](https://qilingtools.com/en/math/nmr): Simulate ¹H NMR spectra at 60–600 MHz from shifts, integrals and J values: splitting trees, multiplicity (t, q, dd, dt), journal peak lists and a shift table. - [Peptide & Protein Calculator](https://qilingtools.com/en/math/peptide): Peptide calculator: formula, monoisotopic and average mass, pI with charge vs pH curve, extinction coefficient, GRAVY, ESI m/z and DNA-to-protein translation. - [Redox Equation Balancer](https://qilingtools.com/en/chemistry/redox-balance): Balance redox equations step by step: half-reaction method in acidic, basic or neutral solution, or the oxidation-number method, with atom and charge checks. - [Lewis Structure Generator](https://qilingtools.com/en/chemistry/lewis): Draw Lewis structures and electron-dot formulas online, with valence electrons, formal charges, resonance, expanded octets, radicals and ionic compounds. - [Buffer Preparation Calculator](https://qilingtools.com/en/chemistry/buffer-prep): Buffer recipe calculator: enter pH, concentration, volume and temperature to get grams of each reagent or mL of HCl/NaOH, with activity correction. - [Solubility Curves](https://qilingtools.com/en/chemistry/solubility-curve): Interactive solubility curves for KNO₃, NaCl, NH₄Cl and 11 more: read values, find intersections, and calculate saturated mass fraction and crystal yields. - [Chromatography Calculator](https://qilingtools.com/en/chemistry/chromatography): Free chromatography calculator: drag a TLC plate for Rf, get k, selectivity, resolution, plate number and Purnell, simulate a chromatogram and plot Van Deemter. - [Lab Replicate Statistics](https://qilingtools.com/en/chemistry/lab-stats): Free analytical chemistry statistics: paste replicates to get mean, SD, RSD and confidence interval, run Dixon's Q, Grubbs, t-tests and the F-test. - [Periodic Table Quiz](https://qilingtools.com/en/chemistry/element-quiz): Free periodic table quiz: symbols, names, positions, atomic numbers, groups, periods and oxidation states, with a timed mode and a mastery heat map. - [Polymer Molecular Weight Calculator](https://qilingtools.com/en/chemistry/polymer): Free polymer calculator: Mn, Mw, Mz, Mv and dispersity from a distribution, degree of polymerization, Carothers equation, Flory distribution and Mark–Houwink. - [3D Molecule Viewer](https://qilingtools.com/en/chemistry/molecule-3d): Free 3D molecule viewer: turn SMILES into a 3D model, rotate and zoom, ball-and-stick or space-filling, measure bond angles and dihedrals, export XYZ or MOL. - [EDTA titration & water hardness](https://qilingtools.com/en/chemistry/edta): Free EDTA titration calculator: αY(H), conditional constant, minimum pH, Ringbom curve, pM titration curve, end-point error and water hardness. - [Redox & precipitation titration curves](https://qilingtools.com/en/chemistry/redox-titration): Free redox titration curve calculator: equivalence potential, jump range and indicator choice for Ce⁴⁺, KMnO₄, dichromate and iodine, plus pAg curves. - [Titrimetric & Gravimetric Calculator](https://qilingtools.com/en/chemistry/volumetric): Free analytical chemistry calculator: standardize titrants with KHP or Na₂CO₃, compute direct, back and indirect titrations, titer and gravimetric factors. - [Ion Tests & Qualitative Analysis](https://qilingtools.com/en/chemistry/qualitative): Free qualitative analysis reference: tests for common cations, anions and gases with equations, an unknown-solution simulator and a test planner. - [Enzyme Kinetics Calculator](https://qilingtools.com/en/chemistry/enzyme-kinetics): Paste [S] and rate data to fit Michaelis–Menten by nonlinear regression: Km, Vmax with 95% CI, kcat, Lineweaver–Burk comparison and inhibition Ki. - [Conductivity Calculator](https://qilingtools.com/en/chemistry/conductivity): Calculate cell constants, molar conductivity, Λm° by Kohlrausch's law, transport numbers and weak acid Ka, plus conductometric titration curves and TDS. - [Bond Polarity Calculator](https://qilingtools.com/en/chemistry/bond-polarity): Get ΔEN, bond type, percent ionic character and the bond dipole for any two elements, decide molecular polarity by 3D vector sum, and compute dipole moments. - [Periodic Trends](https://qilingtools.com/en/chemistry/periodic-trends): Chart ionization energy, electronegativity, atomic radius, electron affinity and melting/boiling points vs atomic number for Z 1–86, with Slater's-rules Zeff. - [Chemical Equations Library](https://qilingtools.com/en/chemistry/reaction-library): Free searchable library of 386 balanced chemical equations from school to general chemistry, with conditions, observations, ionic equations and flash cards. - [Metal Activity Series](https://qilingtools.com/en/chemistry/activity-series): Free reactivity series tool: pick a metal and a solution to see whether displacement happens, with balanced equations, an E° chart and a mixture simulator. - [Electrode reactions (cells & electrolysis)](https://qilingtools.com/en/chemistry/electrode-reactions): Write electrode half-equations: electrolysis by discharge order, lead–acid and Li-ion batteries, fuel cells in any electrolyte, and corrosion of iron. - [Acid–base indicators](https://qilingtools.com/en/chemistry/indicator): Acid–base indicator chart: see 15 indicators' colours at any pH, pick the right indicator for a titration, and compute the In⁻ fraction from pKIn. - [Organic Reactions Map](https://qilingtools.com/en/chemistry/organic-reactions): Interactive functional-group map: reagents, conditions, balanced equations and pitfalls for each reaction, tests for each class, and a shortest-route finder. - [Point Group Finder](https://qilingtools.com/en/chemistry/point-group): Find a molecule's point group: symmetry elements detected from 3D coordinates, the flowchart path, a 3D model with axes and mirror planes, and character tables. - [Crystal Field Theory Calculator](https://qilingtools.com/en/chemistry/crystal-field): Free crystal field calculator: draw the d-orbital splitting diagram and get high/low spin, CFSE, unpaired electrons, magnetic moment and absorbed colour. - [Coordination Compound Naming & Isomers](https://qilingtools.com/en/chemistry/coordination): Free coordination compound tool: get IUPAC and Chinese names, oxidation state, coordination number, geometry, isomers and 18-electron count from a formula. - [Atomic Structure & Average Atomic Mass](https://qilingtools.com/en/chemistry/atomic-structure): Get protons, neutrons and electrons from 23Na+ or Cl-37, average atomic mass and isotope abundances, isotope/allotrope checks and shell diagrams. - [UV–Vis λmax (Woodward–Fieser)](https://qilingtools.com/en/chemistry/uv-vis): Estimate UV λmax of dienes and enones with Woodward–Fieser rules: count substituents, ring residues and exocyclic bonds, add solvent; plus Fieser–Kuhn. - [Conjugate acid–base pairs](https://qilingtools.com/en/chemistry/acid-base-pairs): Free conjugate acid–base pair finder: label Brønsted acids, bases and conjugate pairs in any reaction, predict products and equilibrium direction from pKa. - [Salt hydrolysis & solution balances](https://qilingtools.com/en/chemistry/salt-hydrolysis): Free salt hydrolysis calculator: exact pH and every species' concentration for salts and mixtures, ion ranking, and verified charge, mass and proton balances. - [Reaction Mechanism Simulator](https://qilingtools.com/en/chemistry/mechanism): Simulate reaction mechanisms from elementary steps: concentration–time curves, steady-state and pre-equilibrium rate laws checked against the full kinetics. - [Vapor–Liquid Equilibrium & Distillation](https://qilingtools.com/en/chemistry/distillation): Antoine vapor pressure and boiling point for 20 liquids, Raoult's law T-x-y diagrams, McCabe-Thiele stages, minimum reflux, Fenske and Rayleigh distillation. - [Common Solvent Properties](https://qilingtools.com/en/chemistry/solvents): Boiling point, density, refractive index, dielectric constant and polarity index of 36 lab solvents, plus a miscibility chart and solvent picker. - [Liquid–Liquid Extraction Calculator](https://qilingtools.com/en/chemistry/extraction): Free extraction calculator: single vs multiple extraction recovery from KD, distribution ratio vs pH, acid–base separation, countercurrent and layer order. ### Physics Tools - [Unit Converter](https://qilingtools.com/en/math/unit): Free online unit converter: length, area, volume, weight, temperature, time, speed, data, pressure, energy and angle — one value converts every unit at once. - [Vector Calculator](https://qilingtools.com/en/math/vector): Free online vector calculator for 2D and 3D: addition, scalar multiples, dot and cross products, magnitude, angle, unit vector and projections, with checks. - [Significant Figures Calculator](https://qilingtools.com/en/math/significant-figures): Free online sig fig calculator: count significant figures digit by digit, round to N sig figs or decimals with six rounding modes, and compute by sig fig rules. - [Tone Generator](https://qilingtools.com/en/audio/tone-generator): Free online tone generator: sine, square, sawtooth and triangle waves from 1 to 20,000 Hz, a note picker, sweeps, white/pink/brown noise and a WAV download. - [Audio Spectrogram](https://qilingtools.com/en/audio/spectrogram): Free online spectrogram generator: see time, frequency and level from a Hann-windowed STFT, with FFT size, log axis, dB range and colour maps. Exports PNG. - [Decibel Meter](https://qilingtools.com/en/audio/decibel): Free online decibel meter: measure noise with your mic in real time, A/C/Z weighting, fast/slow response, min/max/average/Leq, 60-second graph and calibration. - [Physics Formula Calculator](https://qilingtools.com/en/physics/physics): Physics formulas solved with steps: SUVAT, projectiles, Newton’s laws, inclines, energy, Ohm’s law, resistors, RC, buoyancy, waves, lenses, gravity. - [Fourier Series & FFT Visualizer](https://qilingtools.com/en/math/fourier): Fourier series coefficients and animated partial sums for square, sawtooth, triangle or any function (Gibbs), draw-your-own epicycles and FFT spectra. - [Differential Equation Solver](https://qilingtools.com/en/math/ode): ODE tool: slope fields with click-to-trace solutions (RK4/RK45), Euler vs RK4 errors, phase portraits with equilibrium types, and 2nd-order linear ODEs. - [Gas Law Calculator](https://qilingtools.com/en/chemistry/gas-law): Free gas law calculator: solve PV=nRT for any variable, combined gas laws, gas density, Dalton's partial pressures, gas over water and van der Waals Z. - [Half-Life Calculator](https://qilingtools.com/en/chemistry/half-life): Solve radioactive decay for any unknown with 30+ isotopes: decay constant, activity in Bq and Ci, carbon-14 dating and first-order kinetics. - [Calorimetry & Specific Heat Calculator](https://qilingtools.com/en/math/calorimetry): Free calorimetry calculator: solve q = mcΔT with a specific heat table, find the final temperature of mixtures, get ΔH from coffee-cup and bomb calorimetry. - [Unit Cells & Crystal Structures](https://qilingtools.com/en/math/crystal): Interactive 3D unit cells (SC, BCC, FCC, HCP, NaCl, CsCl, ZnS, diamond, perovskite) with atoms per cell, coordination number, packing efficiency and density. - [Light Energy & Atomic Spectra](https://qilingtools.com/en/math/spectroscopy): Convert wavelength, frequency and photon energy (eV, J, kJ/mol), compute hydrogen spectral lines, photoelectric stopping potential and de Broglie wavelength. - [Projectile Motion Simulator (with Air Resistance)](https://qilingtools.com/en/physics/projectile): Animated projectile simulator: set speed, angle, height and gravity (Earth, Moon, Mars, Jupiter), add air drag (RK4), compare paths and find the best angle. - [Pendulum & Double Pendulum Simulator](https://qilingtools.com/en/physics/pendulum): Simulate a nonlinear pendulum (RK4) beside its small-angle twin: exact period, damping, phase space and energy plots, plus a chaotic double pendulum. - [Collision Simulator (Momentum & Energy)](https://qilingtools.com/en/physics/collision): Simulate 1D cart collisions with any masses, velocities and restitution e, see momentum and KE before and after, plus 2D billiard collisions. - [Orbit & Gravity Simulator](https://qilingtools.com/en/physics/orbit): Drag a satellite's velocity to get circular, elliptic or hyperbolic orbits with live orbital elements, Kepler's equal areas, N-body demos and Δv tools. - [Lens & Mirror Ray Diagram](https://qilingtools.com/en/physics/optics): Interactive ray diagrams for converging and diverging lenses and concave and convex mirrors: drag the object to see image position, size and magnification. - [Refraction & Total Internal Reflection Simulator](https://qilingtools.com/en/physics/refraction): Drag a light ray through water, glass or diamond: refraction angle, Fresnel reflectance, critical angle, Brewster angle, prism dispersion and apparent depth. - [Wave Superposition & Standing Waves](https://qilingtools.com/en/physics/waves): Interactive wave simulator: superpose traveling waves, see standing waves on strings and pipes with nodes and harmonics, hear beats, and explore a ripple tank. - [Doppler Effect Simulator](https://qilingtools.com/en/physics/doppler): Doppler effect calculator with animation: moving source and observer, Mach cone and sonic boom, relativistic redshift, radar speed guns and pass-by audio. - [Electric Field & Potential Simulator](https://qilingtools.com/en/physics/electric-field): Drag point charges and watch electric field lines and equipotentials update live. Probe E and V anywhere, compute Coulomb forces and launch a test charge. - [Resistor Color Code Calculator](https://qilingtools.com/en/physics/resistor-color): Resistor color code calculator for 4, 5 and 6 bands: value, tolerance and tempco; find bands for any value snapped to E12/E24/E96; decode SMD codes like 472. - [RC / RL / RLC Circuit Simulator](https://qilingtools.com/en/physics/rc-circuit): Simulate RC charging and discharging, RL current and RLC step response with τ marks, plus resonance, Q, bandwidth, filter cutoff, Bode plots and live phasors. - [Special Relativity Calculator & Spacetime Diagram](https://qilingtools.com/en/physics/relativity): Lorentz factor, time dilation and length contraction with a rocket animation, relativistic energy, velocity addition, twin paradox and a Minkowski diagram. - [Blackbody Radiation & Planck's Law Visualizer](https://qilingtools.com/en/physics/blackbody): Plot Planck blackbody curves for several temperatures with Wien peaks, σT⁴ power, visible fraction, blackbody colour and the Rayleigh–Jeans comparison. - [Spring Oscillator & Resonance](https://qilingtools.com/en/physics/spring): Animated spring-mass-damper with driving force: live x(t), damping regime with ω₀, ζ and Q, resonance curves, and coupled normal modes with beats. - [Magnetic Field Simulator](https://qilingtools.com/en/physics/magnetic-field): Drag current-carrying wires and bar magnets to see field lines, compass needles and |B|. Exact loop and solenoid fields, on-axis B(z) and forces between wires. - [Charged Particle in E & B Fields](https://qilingtools.com/en/physics/charged-particle): Electrons, protons or alphas in any uniform E and B in 3D: gyroradius, period, pitch and E×B drift, plus a velocity selector, mass spectrometer and cyclotron. - [Electromagnetic Induction & Generator](https://qilingtools.com/en/physics/induction): Move a magnet through a coil and watch flux, EMF and the galvanometer obey Lenz's law, plus an AC generator, a rod on rails and a transformer. - [DC Circuit Builder & Solver](https://qilingtools.com/en/physics/dc-circuit): Build DC circuits on a grid with batteries, resistors, bulbs, switches and meters. Nodal analysis gives every voltage, current and power, plus KCL/KVL. - [Diffraction, Interference & Polarization](https://qilingtools.com/en/physics/diffraction): Free wave-optics simulator: slit and grating patterns in white light, Airy disks and the Rayleigh limit, thin-film colours, Newton's rings and Malus's law. - [Heat Conduction Simulator](https://qilingtools.com/en/physics/heat-conduction): Simulate heat conduction: animated 1D rod (Crank–Nicolson) with real materials, paintable 2D plate, composite wall U-value calculator and Newton cooling fit. - [Fluid Mechanics Simulator (Bernoulli, Buoyancy, Pipe Flow)](https://qilingtools.com/en/physics/fluid): Interactive fluid mechanics: drag a pipe to see Bernoulli at work, Venturi meter, Torricelli tank draining, buoyancy, Pascal press and Reynolds number. - [Moment of Inertia & Rotational Dynamics](https://qilingtools.com/en/physics/rotation): Moment of inertia for rods, disks, spheres, plates and composites with the parallel-axis theorem; rolling race, spinning skater, Atwood machine. - [Circular Motion & Centripetal Force Simulator](https://qilingtools.com/en/physics/circular-motion): Animated circular motion: velocity and centripetal vectors, cut the string, centrifugal force, banked curves, coaster loops, conical pendulum. - [Quantum Mechanics Simulator (Schrödinger Equation)](https://qilingtools.com/en/physics/quantum): Solve the 1D Schrödinger equation online: energy levels and wavefunctions for wells, oscillators or a drawn potential, plus tunneling wave packets and T(E). - [Heat Engine Cycles & PV Diagrams](https://qilingtools.com/en/physics/thermo-cycle): Interactive PV and TS diagrams for Carnot, Otto, Diesel, Brayton, Stirling and custom cycles. Drag states, see Q, W, ΔU, ΔS per step, efficiency and COP. - [Kinetic Theory of Gases Simulator](https://qilingtools.com/en/physics/gas-kinetics): Watch hundreds of colliding molecules: speed histogram vs Maxwell–Boltzmann, pressure from wall impacts, mean free path, piston heating, effusion and mixing. - [Nuclear Binding Energy, Fission & Fusion](https://qilingtools.com/en/physics/nuclear): Binding energy per nucleon from AME2020 masses, mass defect and SEMF terms for any nuclide, and Q-values for fusion, fission and decay vs TNT and coal. - [Simple Machines Simulator (Levers, Pulleys, Gears)](https://qilingtools.com/en/physics/simple-machines): Drag a lever’s fulcrum, lift loads with pulleys, mesh gear trains and bike gears, and compare inclines, screw jacks and wedges: force and efficiency. - [Free-Body Diagrams & Force Vectors](https://qilingtools.com/en/physics/forces): Interactive free-body diagrams: add and resolve force vectors, solve a block on an incline with friction and a pulley, rope tensions and the ladder problem. - [Beam Shear & Bending Moment Calculator](https://qilingtools.com/en/physics/beam): Free beam calculator: simple, overhanging and cantilever beams with point, distributed and triangular loads. Reactions, shear and moment diagrams, deflection. - [Capacitor Simulator](https://qilingtools.com/en/physics/capacitor): Slide a dielectric into a parallel-plate capacitor and see C, Q, V, E and energy change. Plus cylindrical and spherical capacitors and series-parallel networks. - [Logic Circuit Simulator](https://qilingtools.com/en/physics/logic-circuit): Build digital logic circuits in your browser: gates, flip-flops, switches, LEDs and 7-segment displays, with live simulation, truth tables and timing diagrams. - [Acoustics Calculator (RT60, Room Modes, Decibels)](https://qilingtools.com/en/physics/acoustics): Room acoustics online: Sabine & Eyring RT60 from room size and materials, room modes, dB addition, distance loss, A-weighting, noise dose, speed of sound. - [Color of Light Simulator (Additive & Subtractive)](https://qilingtools.com/en/physics/color-light): Mix red, green and blue spotlights, stack cyan, magenta and yellow filters, and see objects under sodium, LED or tungsten light via spectra and CIE 1931. - [Eye Optics Simulator (Myopia, Hyperopia, Astigmatism)](https://qilingtools.com/en/physics/eye): Reduced-eye ray diagrams for myopia, hyperopia, astigmatism and presbyopia, a blurred eye chart, far/near points, glasses vs contacts power, Rx reader. - [Rocket Equation & Launch Simulator](https://qilingtools.com/en/physics/rocket): Rocket equation calculator: get Δv from Isp and mass ratio, design multi-stage rockets, compare Δv budgets, and simulate a gravity-turn launch with Max-Q. - [Lagrange Points](https://qilingtools.com/en/physics/lagrange-points): Lagrange point simulator: find L1–L5 for Sun–Earth, Earth–Moon and Sun–Jupiter, map the effective potential and zero-velocity curves, launch test particles. - [Chaos & Strange Attractors](https://qilingtools.com/en/physics/chaos): Explore chaos: logistic map cobwebs and zoomable bifurcation diagram, Lyapunov exponent, Feigenbaum constant, 3D Lorenz attractor and Poincaré sections. - [Error Propagation & Uncertainty Calculator](https://qilingtools.com/en/physics/error-propagation): Propagate uncertainty through any formula: enter values ± errors to get the result, partial derivatives, error budget, Monte Carlo check and weighted line fit. - [Chladni Patterns & Drum Modes](https://qilingtools.com/en/physics/chladni): Chladni pattern simulator: sweep the frequency and watch sand gather on nodal lines, play the tone, animate drum Bessel modes and mix degenerate modes. - [Physical Constants Table (CODATA 2022)](https://qilingtools.com/en/physics/constants): Searchable CODATA 2022 physical constants: c, h, electron mass, fine-structure constant and 100+ more with uncertainties. Copy as LaTeX or code, convert units. - [Dimensional Analysis Tool](https://qilingtools.com/en/physics/dimensions): Check if a physics equation is dimensionally consistent, simplify units like kg·m²/s³/A to V, find dimensionless groups with Buckingham π, see Planck units. - [Ising Model Simulator](https://qilingtools.com/en/physics/ising): Live 2D Ising model: Metropolis and Wolff Monte Carlo, energy, magnetisation, specific heat, susceptibility, T scans vs Onsager's solution, hysteresis. - [Brownian Motion & Diffusion Simulator](https://qilingtools.com/en/physics/random-walk): Simulate Brownian motion: thousands of random walkers, Langevin dynamics, MSD slope fits, Lévy flights and subdiffusion, Stokes–Einstein D and Fick's law. - [H-R Diagram & Stellar Evolution](https://qilingtools.com/en/physics/hr-diagram): Interactive Hertzsprung-Russell diagram with 80+ famous stars in blackbody colours, constant-radius lines, a main-sequence calculator and evolution tracks. - [Cosmology Calculator](https://qilingtools.com/en/physics/cosmology): ΛCDM cosmology calculator: from H₀, Ωm, ΩΛ and redshift get age, lookback time and comoving, luminosity and angular-diameter distances, with a(t) and H(z). - [Black Holes & Gravitational Lensing](https://qilingtools.com/en/physics/black-hole): Black hole calculator: Schwarzschild radius, photon sphere, ISCO, shadow size, Hawking temperature, evaporation time and tides, with orbit and lensing demos. - [Solar System Simulator](https://qilingtools.com/en/physics/solar-system): Solar System orrery: planet positions for any date 1800–2050 from JPL Keplerian elements, with distances, elongations, opposition dates and a scale model. - [Electromagnetic Waves & Polarization](https://qilingtools.com/en/physics/em-wave): Animated 3D EM plane wave with E and B, intensity and radiation pressure calculator, Jones-matrix polarization, Poincaré sphere and an EM spectrum explorer. - [Semiconductors & PN Junctions](https://qilingtools.com/en/physics/semiconductor): PN junction band diagrams for Si, Ge and GaAs with built-in potential and depletion width, diode I–V with series resistance, LED colours and solar cells. - [Op-Amp Circuit Calculator](https://qilingtools.com/en/physics/op-amp): Op-amp calculator with schematics: inverting, non-inverting, summing, difference, instrumentation, Sallen–Key, Schmitt trigger, plus Bode plots and E24 design. - [Materials Properties & Stress–Strain Curves](https://qilingtools.com/en/physics/materials): Compare stress–strain curves of 15 materials with an animated tensile test: E, yield, UTS, toughness. Axial load, thermal stress, bimetal strip and Ashby chart. - [Surface Tension & Capillarity](https://qilingtools.com/en/physics/capillary): Surface tension calculator: animated Jurin capillary rise, Laplace pressure of drops and soap bubbles, drop shapes, Stokes' law settling and a floating needle. - [Radiation Dose & Shielding Calculator](https://qilingtools.com/en/physics/radiation-dose): Learn radiation dose: convert Gy, Sv, rem, R, Bq and Ci, ICRP 103 effective dose, a log-scale dose chart, point-source dose rates, HVL and alpha/beta range. - [Gyroscope & Spinning Top Simulator](https://qilingtools.com/en/physics/gyroscope): 3D heavy symmetric top simulator: RK4 rigid-body motion with precession and nutation (cusps, waves, loops), sleeping-top threshold and a bicycle-wheel gyro. - [Tides & Roche Limit Explorer](https://qilingtools.com/en/physics/tides): Explore tides: tidal force field and bulge, spring and neap tides, M2/S2/K1/O1 tide curves, an animated Roche-limit breakup and lunar recession vs day length. - [DC Motor Simulator & Torque–Speed Curves](https://qilingtools.com/en/physics/motor): Interactive DC motor: animated commutator and Lorentz force, torque ripple, speed, current and efficiency, torque–speed curves and start-up inrush current. - [AC Power & Power Factor Calculator](https://qilingtools.com/en/physics/ac-power): AC power calculator: P, Q, S and power factor with waveforms, PF-correction capacitors, star/delta three-phase with neutral current, energy bills and THD. - [Gauss’s Law Visualizer & Field Calculator](https://qilingtools.com/en/physics/gauss-law): Visualize Gauss’s law for spheres, shells, coaxial cables, planes and plates: drag the Gaussian surface, see enclosed charge and flux, and plot E(r) and V(r). - [Wave Pulse on a String: Reflection & Transmission](https://qilingtools.com/en/physics/wave-pulse): Pulses on a string: inverted or upright reflection at a junction, measured r and t vs theory, fixed, free and absorbing ends, colliding pulses, standing waves. - [Laser physics simulator](https://qilingtools.com/en/physics/laser): Laser simulator: animated 2/3/4-level atoms show inversion; rate equations give threshold, L–I curve, spiking and Q-switching; cavity modes and Gaussian beams. - [Particle physics & the Standard Model](https://qilingtools.com/en/physics/particle-physics): Interactive Standard Model chart (PDG 2024 masses), quark hadron builder, conservation-law checker for reactions, two-body decay and invariant-mass calculator. - [Earth's Energy Balance & Greenhouse Effect Simulator](https://qilingtools.com/en/physics/climate-energy): Planetary energy balance lab: effective temperature, N-layer greenhouse model, global energy budget diagram, CO₂ forcing, two-box warming and spectra. - [Entropy & microstates](https://qilingtools.com/en/physics/entropy): Interactive statistical entropy: coin macrostates, Einstein solids and temperature, free expansion ΔS = Nk ln 2, Boltzmann levels and Maxwell's demon. - [Energy Skate Park](https://qilingtools.com/en/physics/energy-track): Skate park energy simulator: draw your own track, try loop, ski jump and double-well presets, add friction and drag, and watch live KE, PE and heat bars. - [Relative Motion & Reference Frames](https://qilingtools.com/en/physics/relative-motion): Relative velocity simulator: river crossing (min time vs min drift), aircraft wind triangle, rain seen from a moving car, and closest approach of two ships. - [Motion Graphs (x-t, v-t, a-t)](https://qilingtools.com/en/physics/motion-graphs): Build a motion by dragging the v-t graph and see synced x-t and a-t graphs with tangent slope and area, plus a graph-matching game and translation drills. - [Normal Modes & Lattice Vibrations](https://qilingtools.com/en/physics/normal-modes): Normal modes of a mass-spring chain (1–30 masses; fixed, free or periodic ends): mode animation, superposition, dispersion, diatomic band gap and wave packets. - [Fiber Optics Simulator](https://qilingtools.com/en/physics/fiber-optics): Fiber optics simulator: trace TIR rays by dragging the launch angle, find NA and acceptance angle, V-number and modes, bend loss, link budget and dispersion. - [Telescope Calculator](https://qilingtools.com/en/physics/telescope): Telescope calculator: magnification, true field, exit pupil, resolution, limiting magnitude, a to-scale eyepiece view and astrophoto sampling. - [Hydrogen Atom Orbitals](https://qilingtools.com/en/physics/hydrogen-atom): Plot exact hydrogen wavefunctions ψnlm up to n = 7: phase cross-sections with nodes, a 3D electron cloud, radial r²R², levels and sloshing superpositions. - [X-ray Physics: Tube Spectrum, Bragg & Compton](https://qilingtools.com/en/physics/xray): X-ray tube spectra with Kα/Kβ lines and filters, Moseley’s law, Bragg diffraction with powder patterns, and Compton scattering with Klein–Nishina plots. - [Coriolis Effect & Foucault Pendulum](https://qilingtools.com/en/physics/coriolis): See the Coriolis force on a turntable from both frames, compute shell and falling-object deflection, cyclones, inertial circles and Foucault precession. - [Vehicle Dynamics: Braking, Crashes & Cornering](https://qilingtools.com/en/physics/vehicle-dynamics): Car physics: stopping distance by speed, reaction time and road with animation, crash g-forces, cornering and rollover limits, 0–100 time and energy use. - [Magnus Effect: Spinning Ball Trajectories](https://qilingtools.com/en/physics/magnus): Simulate spinning balls in 3D with drag and Magnus lift: banana kick, curveball, topspin and golf presets, no-spin comparison and spinning-cylinder flow. - [Atmosphere & Altitude Calculator](https://qilingtools.com/en/physics/atmosphere): ISA 1976 standard atmosphere: temperature, pressure, density and sound speed at any altitude, altitude from pressure, boiling point, oxygen, dew point. - [Water Waves & Ocean Waves](https://qilingtools.com/en/physics/water-waves): Water waves: phase and group speed from wavelength or period and depth, orbit animation, wave power, tsunami travel time, shoaling, breaking, wind seas. - [Seismic Waves & Earthquake Magnitude](https://qilingtools.com/en/physics/seismology): Animate P, S, Rayleigh and Love waves, locate an epicentre from S−P times, compute Richter and moment magnitude and energy, and trace rays through the Earth. - [Rainbow Formation Simulator](https://qilingtools.com/en/physics/rainbow): Trace light through a raindrop, get the 42° primary and 51° secondary bows from water's dispersion, render a double rainbow, see polarization and halos. - [Light Scattering & Sky Colour](https://qilingtools.com/en/physics/scattering): Rayleigh scattering simulator: render the sky from noon to twilight, see why it is blue not violet, why clouds are white and how skylight is polarized. - [Solar Position, Irradiance & PV Yield Calculator](https://qilingtools.com/en/physics/solar-energy): Find solar elevation, azimuth, sunrise, sunset and the sun path for any place and date, clear-sky irradiance on a tilted panel, optimal tilt and rough PV yield. - [Wind Power Calculator - Betz Limit & Turbine Energy](https://qilingtools.com/en/physics/wind-power): Calculate wind power ½ρAv³, see the Betz limit derived on an animated actuator disk, design a turbine power curve and estimate annual energy from Weibull winds. - [Battery Capacity, Runtime & Pack Calculator](https://qilingtools.com/en/physics/battery): Convert mAh to Wh, work out battery runtime, C-rate and charge time, see why power banks quote 3.7 V, build nSmP packs and check the 100 Wh airline limit. - [Magnetic Materials & Hysteresis](https://qilingtools.com/en/physics/magnetic-materials): Simulate B–H loops and losses for silicon steel, ferrite and NdFeB, watch domain avalanches, compare dia-, para- and ferromagnets, estimate magnet pull. - [String Instrument Physics: Tension & Fret Calculator](https://qilingtools.com/en/physics/guitar-strings): String tension for guitar, bass, ukulele and violin sets, printable fret tables, how the pluck point shapes harmonics, and piano inharmonicity. - [Phase diagrams & phase transitions](https://qilingtools.com/en/physics/phase-diagram): Interactive P–T phase diagrams for water, CO₂ and nitrogen: drag a state point, animate pressure cooking and freeze-drying, try Clausius–Clapeyron and vdW. - [Static Electricity & Lightning](https://qilingtools.com/en/physics/electrostatics): Triboelectric series, electroscope induction animation, charge sharing between spheres, Paschen breakdown and spark length, corona at points, thunder distance. - [Smith Chart & Impedance Matching](https://qilingtools.com/en/physics/smith-chart): Interactive Smith chart: click or type a load to get Γ, VSWR and return loss, rotate along a line, design stub and L-network matches, sweep RLC loads. - [Antenna Patterns & Arrays](https://qilingtools.com/en/physics/antenna): Exact dipole/monopole patterns, directivity and radiation resistance; phased-array steering with Chebyshev tapers; Friis link budget; antenna length by band. - [Flight Physics Simulator (Lift, Stall & Aircraft Performance)](https://qilingtools.com/en/physics/flight): Interactive flight physics: NACA airfoils with potential-flow animation, lift curve and stall, stall speed, glide range, power curve, turn g and climb forces. - [Skydiving Simulator (Terminal Velocity & Opening Shock)](https://qilingtools.com/en/physics/skydiving): Skydiving simulator with air density varying by altitude, body positions, canopy opening and transonic drag. Recreates Baumgartner; compares terminal speeds. - [Hot-Air & Helium Balloon Lift Calculator](https://qilingtools.com/en/physics/balloon): Balloon physics calculator: hot-air lift, payload and equilibrium altitude with an ascent animation, lifting gases, helium balloons per person, burst altitude. - [G-Force & Apparent Weight Calculator](https://qilingtools.com/en/physics/g-force): G-force calculator: elevator scale readings incl. free fall, coaster loop and airtime g, space-station artificial gravity, human tolerance chart and g from Δv. - [Human biomechanics](https://qilingtools.com/en/physics/biomechanics): Physics of the body: jump height to takeoff speed, force and power; Froude number and walk–run speed; cycling power and climb time; MET calories; biceps force. - [Exoplanet Detection Simulator](https://qilingtools.com/en/physics/exoplanet): Transit light curves with limb darkening and noise, radial-velocity curves and Doppler shifts, and Kopparapu habitable zones with planet temperatures. - [Solar & Lunar Eclipses](https://qilingtools.com/en/physics/eclipse): See why eclipses are total or annular with real Sun, Moon and Earth sizes: shadow cones, magnitude, lunar eclipse durations, Saros series and a 2026–2035 table. - [Moon Phase Calculator](https://qilingtools.com/en/physics/moon-phase): Moon phase for any date and city: illumination, age, distance, a correctly oriented Moon image, a monthly phase calendar, full/new moon times and moonrise. - [Your Weight on Other Planets](https://qilingtools.com/en/physics/planet-weight): Enter your weight in kg, lb or jin to see it on the Moon, Mars, Jupiter, Pluto or a neutron star, plus jump height, fall time, throw range and escape velocity. - [Thin-Film Interference & Interferometers](https://qilingtools.com/en/physics/interference): Spectrally computed soap bubble and oil film colours, a draining soap film, AR coating designer, Newton's rings radius fit and a Michelson interferometer. - [Photoelectric Effect Lab](https://qilingtools.com/en/physics/photoelectric): Virtual photoelectric lab: choose a metal, wavelength, intensity and bias, watch photoelectrons and the I–V curve, and fit Planck's constant. - [Camera Optics: Depth of Field & Exposure](https://qilingtools.com/en/physics/camera-optics): Photography optics calculator: depth of field, hyperfocal distance, field of view, exposure triangle, motion blur, NPF star rule, diffraction limit and bokeh. - [Scuba Diving Physics Calculator](https://qilingtools.com/en/physics/scuba): Dive physics online: pressure and Boyle's law animation, SAC and rule of thirds, nitrox MOD and best mix, buoyancy and weighting, ZHL-16C no-deco demo. - [Gravitational Wave Simulator (Binary Inspiral & Chirp)](https://qilingtools.com/en/physics/gravitational-waves): Enter two masses and a distance to get chirp mass, time to merger and the strain waveform h(t), see a ring of particles stretch, and hear the chirp. - [Sonar, Radar & Echolocation](https://qilingtools.com/en/physics/sonar-radar): Animated echo ranging and range resolution, bat Doppler, ocean sound speed and ray bending, radar equation range and PPI scope, speed radar, ultrasound depth. - [Earth’s Magnetic Field & Aurora (Dipole, Declination, Van Allen Belts)](https://qilingtools.com/en/physics/geomagnetism): Tilted-dipole model of Earth’s field: declination, inclination and strength anywhere, magnetosphere and Van Allen belts, and where Kp lets you see aurora. - [Superconductivity Simulator](https://qilingtools.com/en/physics/superconductivity): Resistance drop at T_c for real superconductors, Meissner field lines, type I/II phase diagram and vortex lattice, London depth, flux-pinning levitation, MRI. - [Gravity Assist & Interplanetary Transfer Simulator](https://qilingtools.com/en/physics/gravity-assist): Simulate a gravity assist: set v∞ and periapsis to see the turn angle and Sun-frame speed gain, then get Hohmann Δv, flight time and launch windows. - [Wire Size & Voltage Drop Calculator](https://qilingtools.com/en/physics/wire-sizing): Voltage drop for DC, 1- and 3-phase; smallest cable size by drop limit and ampacity (mm², AWG), loss cost, breaker hint, 12 V solar and LED strips. - [Thermal Expansion Calculator](https://qilingtools.com/en/physics/thermal-expansion): Linear, area and volume expansion, expansion joints, rail stress and buckling, bimetallic thermostat, shrink fits, liquids and the 4 °C water anomaly. - [Heat Pump & Air Conditioner Calculator](https://qilingtools.com/en/physics/heat-pump): Animated heat pump / AC cycle with P–h diagram, Carnot vs real COP, heat pump vs electric vs gas heating cost, AC sizing in W, BTU/h and HP. - [Brachistochrone Race (Cycloid vs Line, Arc, Parabola)](https://qilingtools.com/en/physics/brachistochrone): Drag the endpoints and race beads down a line, circular arc, cycloid, parabola and your own curve, add friction, and explore the tautochrone and Snell analogy. - [Nuclear Fission Reactor Simulator](https://qilingtools.com/en/physics/fission-reactor): Neutron chain reaction and criticality, fission energy vs fuels, six-factor formula, point kinetics with delayed neutrons, decay heat and PWR efficiency. - [Polarization & Birefringence Simulator](https://qilingtools.com/en/physics/polarization): Jones-calculus optical bench: drag polarizers and wave plates, see the E-field ellipse and Poincaré sphere; Brewster angle, calcite, interference colors, LCDs. - [Microscope Resolution & Imaging Calculator](https://qilingtools.com/en/physics/microscope): Microscope calculator: Abbe and Rayleigh resolution from NA and wavelength, Airy-disk demo, useful magnification, camera sampling, phase contrast, STED, EM. - [Ripple Tank Simulator](https://qilingtools.com/en/physics/ripple-tank): Real-time 2D ripple tank: place sources, draw walls and slits; single and double slit, gratings, refraction, lens focus, standing waves and Mach cones. - [Wind Instruments & Resonance Tube Calculator](https://qilingtools.com/en/physics/pipe-acoustics): Open, closed and conical pipe resonances with end correction and standing-wave animation; flute vs clarinet, tone holes, resonance tube, bottles, organ pipes. - [Neutron Stars & Pulsars](https://qilingtools.com/en/physics/neutron-star): Compare white dwarfs, neutron stars and black holes, see light bending, watch and hear a pulsar, get age and B-field from P and Ṗ, and distance from DM. - [How GPS Works](https://qilingtools.com/en/physics/gps): Drag satellites and a receiver to see how pseudoranges solve position and clock error and why 4 satellites are needed; constellation, DOP, relativity and RTK. - [Space Elevator](https://qilingtools.com/en/physics/space-elevator): Space elevator physics: net acceleration vs altitude, taper ratio by material, climb time and energy, release orbits, counterweight, Moon and Mars. - [Atmospheric Reentry Simulator](https://qilingtools.com/en/physics/reentry): Simulate spacecraft reentry: set speed, entry angle, ballistic coefficient and L/D to get altitude, speed, g-load and heat flux, plus the entry corridor. - [Nuclear fusion & tokamaks](https://qilingtools.com/en/physics/fusion): Interactive fusion explorer: D-T, D-D, p-B11 reactivity, Gamow peak, Lawson triple product and ignition, tokamak and laser implosion animations, Q gain. - [MRI physics simulator](https://qilingtools.com/en/physics/mri): Interactive MRI physics: Larmor precession, RF flip, T1/T2 relaxation, TR/TE weighting on a synthetic brain, spin-echo animation, k-space FFT reconstruction. - [Hydropower calculator](https://qilingtools.com/en/physics/hydropower): Hydropower calculator: P = ηρgQH, turbine selection, penstock loss and economic diameter, annual energy from flow duration, pumped storage, dam pressure. - [Power grid simulator](https://qilingtools.com/en/physics/power-grid): Power grid physics: high-voltage line loss, AC vs HVDC breakeven, duck-curve dispatch, frequency drop after a trip with load shedding, three-phase, PF. - [Virtual Wind Tunnel (2D Flow Simulation)](https://qilingtools.com/en/physics/wind-tunnel): Live 2D lattice Boltzmann wind tunnel: vortex streets, airfoils, cars and buildings. Draw obstacles, view vorticity, get drag, lift and Strouhal number. - [Truss Solver (2D Truss Analysis)](https://qilingtools.com/en/physics/truss): 2D truss calculator: draw nodes, members, supports and loads. Get member forces, reactions and deflection, check stability and buckling, see joint steps. - [Live Sky Chart](https://qilingtools.com/en/physics/sky-chart): Free live sky chart for any city or latitude and time: 1,267 bright stars, 51 constellations, the Sun, Moon and planets, and rise, transit and set times. - [Sundial Designer](https://qilingtools.com/en/physics/sundial): Design horizontal, vertical or equatorial sundials for your latitude: hour-line angles, gnomon angle, printable SVG, equation of time and clock conversion. - [Asteroid Impact Simulator](https://qilingtools.com/en/physics/asteroid-impact): Asteroid impact calculator (Collins et al. 2005): energy in Mt TNT, airburst or crater, crater size, fireball, earthquake, blast radius and tsunami. - [Wireless charging & induction cooktops](https://qilingtools.com/en/physics/wireless-power): Compute coil mutual inductance and coupling k, simulate resonant wireless power and frequency splitting, align a Qi phone, see why hobs need iron pans. - [How a microwave oven heats](https://qilingtools.com/en/physics/microwave-oven): Simulate cavity standing waves, hot spots and turntable heating, measure light speed with chocolate, see dielectric loss and penetration depth, metal sparks. - [Tesla coil](https://qilingtools.com/en/physics/tesla-coil): Design a spark-gap Tesla coil: primary and secondary inductance, top-load capacitance, resonance and tap point, energy transfer, voltage and spark length. - [Loudspeakers, enclosures & noise cancelling](https://qilingtools.com/en/physics/loudspeaker): Enter Thiele–Small parameters, design sealed and ported boxes with response, impedance and excursion plots, port length and air speed, crossovers and ANC. - [Trebuchet Simulator](https://qilingtools.com/en/physics/trebuchet): Counterweight trebuchet physics: Lagrangian RK4 model of ground slide, sling swing and release, drag flight, range, efficiency, sweeps and onager comparison. - [Archery Physics Calculator](https://qilingtools.com/en/physics/archery): Bow physics: draw-force curve to stored energy and arrow speed for longbow, recurve and compound bows, KE, momentum, trajectory, sight marks, drift, spine. - [Bicycle Physics Calculator](https://qilingtools.com/en/physics/bicycle): Bike physics: gear ratios and speed per cadence, power vs speed with rolling, aero and gradient, climb times and W/kg, Whipple self-stability, braking limits. - [Sailing Physics: Apparent Wind, Sail Forces & Polars](https://qilingtools.com/en/physics/sailing): How sailing upwind works: draggable apparent-wind triangle, sail lift and drag split into drive and heel, keel leeway, polar diagram, VMG, heel, hull speed. - [Earthquake-resistant buildings & dampers](https://qilingtools.com/en/physics/seismic-isolation): Simulate a multi-storey building in an earthquake: mode shapes, Newmark time history, response spectrum, base isolation and tuned mass dampers (Taipei 101). - [Harmonograph & Lissajous figures](https://qilingtools.com/en/physics/harmonograph): Harmonograph simulator: 2–4 damped pendulums draw colourful curves; set ratios, detune and damping, export PNG/SVG. Also Lissajous figures and interval tones. - [Non-Newtonian fluids](https://qilingtools.com/en/physics/non-newtonian): Explore non-Newtonian fluids: power-law, Bingham, H-B and Carreau curves with presets, plug flow in pipes, oobleck stiffening, ketchup yield and thixotropy. - [Vernier Caliper & Micrometer Reading](https://qilingtools.com/en/physics/vernier-caliper): Interactive vernier caliper and micrometer: drag the slider or thimble, zoom in, see each reading explained with zero error, and practise with instant marking. - [Ticker Tape Timer Analysis](https://qilingtools.com/en/physics/ticker-tape): Simulate a ticker-tape timer: generate tapes, measure counting points, get speeds and acceleration by successive differences, plot v–t and cut-tape charts. - [Meter Conversion & Electrical Measurements](https://qilingtools.com/en/physics/meter-conversion): Convert a galvanometer to an ammeter or voltmeter, explore the ohmmeter scale, voltmeter–ammeter errors, EMF and internal r, bridge and half-deflection. - [Conveyor Belt & Block-on-Board Models](https://qilingtools.com/en/physics/conveyor-belt): Conveyor-belt and block-on-board friction problems: phase-by-phase forces, common speed, v–t graphs, relative sliding and heat, with practice. - [Virtual Oscilloscope](https://qilingtools.com/en/physics/oscilloscope): Online dual-channel oscilloscope simulator: volts/div, time/div, coupling, trigger level and slope, X-Y Lissajous mode, built-in function generator and cursors. - [Transistor Amplifier & Switch Simulator](https://qilingtools.com/en/physics/transistor): NPN BJT simulator: output curves, load line, draggable Q-point and operating regions, CE amplifier bias, gain and clipping, plus BJT and MOSFET switch design. - [555 Timer Calculator & Simulator](https://qilingtools.com/en/physics/timer-555): 555 timer calculator with an animated internal diagram synced to the capacitor and output waveforms: astable, monostable and a standard-value parts picker. - [Sampling Theorem & Aliasing Simulator](https://qilingtools.com/en/physics/sampling): Interactive sampling theorem demo: sinc and zero-order-hold reconstruction, alias frequency and folding, spectral images, wagon-wheel effect, quantization. - [Spin & the Stern–Gerlach experiment](https://qilingtools.com/en/physics/stern-gerlach): Chain Stern–Gerlach analysers at any angle, fire atoms and compare counts with cos²(Δθ/2). Classical vs quantum screens, spin 1, Bloch spheres, CHSH test. - [Quantum statistics & heat capacity of solids](https://qilingtools.com/en/physics/quantum-statistics): Compare Maxwell-Boltzmann, Fermi-Dirac, Bose-Einstein occupation with animated particles; get Fermi energy, BEC transition temperature, Debye heat capacity. - [Pendulum wave](https://qilingtools.com/en/physics/pendulum-wave): Pendulum wave simulator: N pendulums with L = g(Γ/2π(N₀+k))², 3D animation of snakes, rows and realignment, large-angle effects and a DIY length table. - [Typhoon & Hurricane Physics](https://qilingtools.com/en/physics/hurricane): Holland wind profile from central pressure and radius of max winds: wind radii, Saffir-Simpson and China typhoon grades, potential intensity, surge, wind load. - [Volcano Eruption Physics](https://qilingtools.com/en/physics/volcano): Eruption column height from mass eruption rate with VEI, magma viscosity and bubble growth to fragmentation, volcanic bomb trajectories with drag, lava speed. - [Radio Propagation & the Ionosphere](https://qilingtools.com/en/physics/radio-propagation): Chapman-layer ionosphere and plasma frequency, sky-wave ray tracing with hops and skip zone, MUF, skip distance, D-layer absorption, radio horizon, path loss. - [Household Circuits & Electrical Safety](https://qilingtools.com/en/physics/household-circuit): Interactive house wiring: plug in appliances to trip the breaker, read the energy meter and bill, use a test pen, compare shocks and RCDs, with quizzes. - [Circuit Dynamics Analyzer](https://qilingtools.com/en/physics/circuit-dynamics): Move a rheostat or change an LDR or thermistor and watch every meter in a circuit with internal resistance update; output power, capacitors, faults, practice. - [Rail Induction Models](https://qilingtools.com/en/physics/rail-induction): Conducting rods on rails in a magnetic field: coasting, constant force or power, capacitor, incline and two-rod models with v–t, i–t, energy and analysis. - [Hall Effect & Crossed-Field Devices](https://qilingtools.com/en/physics/hall-effect): Hall effect animation with Hall voltage, carrier type and density, plus velocity selector, MHD generator, flowmeter, mass spectrometer, cyclotron and practice. - [Momentum Conservation Models](https://qilingtools.com/en/physics/momentum-models): Animated classic momentum problems: bullet and block, block on board, spring pair, person and boat, ball on an arc slot, explosions, with energy bars. - [Trapped Gas Columns & Pistons](https://qilingtools.com/en/physics/gas-column): Gas law problems: mercury column in a tilted tube, U-tube with added mercury, piston with stops or springs, two chambers, with p–V graphs and first law. - [Wave and Vibration Graphs](https://qilingtools.com/en/physics/wave-graphs): Synchronised wave (y–x) and vibration (y–t) graphs with direction rules, multiple-solution problems, two-source interference, standing waves and quizzes. - [Heating Curves & Specific Heat](https://qilingtools.com/en/physics/heating-curve): Heating curve of ice to steam with a particle model, crystalline vs amorphous solids, specific heat, mixing, fuel efficiency, a four-stroke engine and quizzes. - [Cavendish Experiment Simulator](https://qilingtools.com/en/physics/cavendish): Virtual Cavendish torsion balance: damped oscillation, optical-lever readings, turning-point analysis, G with corrections, weighing the Earth, Coulomb balance. - [Millikan Oil Drop Experiment](https://qilingtools.com/en/physics/oil-drop): Virtual Millikan oil drop lab: balance a drop, time its fall in the eyepiece, get radius and charge with Cunningham correction, then find e from a histogram. - [Rutherford Scattering Simulator](https://qilingtools.com/en/physics/rutherford): Rutherford gold foil experiment: alpha hyperbolas vs impact parameter, detector counts vs the Rutherford formula and Thomson model, and nuclear size limits. - [Franck–Hertz Experiment Simulator](https://qilingtools.com/en/physics/franck-hertz): Franck–Hertz tube simulation with mercury or neon: inelastic collisions, anode current vs accelerating voltage, peak spacing, excitation energy and wavelength. - [Speed of Light History](https://qilingtools.com/en/physics/speed-of-light): Interactive history of measuring c: Galileo's lanterns, Rømer's Io eclipses, aberration, Fizeau's wheel, Foucault's mirror, Michelson and Michelson–Morley. - [Holography Simulator](https://qilingtools.com/en/physics/holography): Simulate holography: place points, record fringes, refocus via FFT angular spectrum, compare in-line vs off-axis, cut the plate, draw a Fourier hologram. - [Vertical Circular Motion](https://qilingtools.com/en/physics/vertical-circle): Circular-motion exam models: string vs rod critical speeds, leaving the circle, loop-the-loop, turntable, conical pendulum, banked curves and bridges. - [Satellite Orbits & Binary Stars](https://qilingtools.com/en/physics/celestial-exam): Gravitation exam models: orbit comparison, GM = gR², geostationary orbit, cosmic speeds, orbit transfer, satellite chase, binary stars, mass and density. - [Connected Bodies & Instant Acceleration](https://qilingtools.com/en/physics/connected-bodies): Connected bodies with Newton’s 2nd law: strings, pushes, pulleys, stacked-block slipping, spring vs string instant acceleration, elevator readings. - [Vehicle Start-up (Power vs Acceleration)](https://qilingtools.com/en/physics/vehicle-startup): Car start-up exam model: constant power vs constant acceleration, v–t, a–t, P–t and F–t graphs, top speed, work–energy distance, uphill driving. - [Charged Particle Acceleration & Deflection](https://qilingtools.com/en/physics/deflection-tube): Charged particles in electric fields: accelerate with qU₁ = ½mv₀², deflect by y = U₂L²/(4U₁d), find the screen spot, plus CRT sweep, AC plates and practice. - [Charged Particles in a Bounded Magnetic Field](https://qilingtools.com/en/physics/bounded-magnetic-field): Charged particles in bounded magnetic fields: edge, strip, rectangle, circle, triangle, step-by-step centre finding, dynamic circles and focusing. - [Combined Electric, Magnetic & Gravitational Fields](https://qilingtools.com/en/physics/combined-fields): Charged particles in combined fields: exact paths in E, B and gravity (line, circle, cycloid), equivalent gravity on a string, and multi-region analysis. - [Solar Sail & Radiation Pressure](https://qilingtools.com/en/physics/solar-sail): Solar sail simulator: radiation pressure I/c vs 2I/c, oblique force, lightness number, spiral orbits at the 35° optimum and the Starshot laser sail. - [Pressure & Communicating Vessels](https://qilingtools.com/en/physics/pressure): Middle-school pressure lab: bricks on a sponge, a U-tube gauge probe, vessel shapes, communicating vessels, ship lock, hydraulics, Torricelli and practice. - [Density Lab](https://qilingtools.com/en/physics/density-lab): Virtual density lab: level a beam balance and read the rider, read a measuring cylinder, six density methods, error analysis, m-V graphs and quizzes. - [Electromagnets & Relays](https://qilingtools.com/en/physics/electromagnet): Middle-school electromagnetism: Oersted's experiment, solenoid poles and field lines, electromagnet strength, relay alarms, electric bell, motor and generator. - [Ohm’s Law & Lamp Power Lab](https://qilingtools.com/en/physics/ohm-law-lab): Virtual school electricity lab: current vs voltage and resistance, measuring resistance and lamp power, with wiring mistakes and faults explained. - [Reflection & Plane Mirrors](https://qilingtools.com/en/physics/plane-mirror): Interactive school optics: test the law of reflection, specular vs diffuse reflection, plane mirror images, two mirrors, periscope and pinhole camera. - [Convex Lens Lab](https://qilingtools.com/en/physics/lens-lab): Virtual optical bench: move the candle, lens and screen to find a sharp image, measure focal length, learn the lens rules and correct short and long sight. ### Productivity - [QiLing Mind](https://qilingtools.com/en/mindmap): QiLing Mind is a free online mind map editor: add nodes with Tab/Enter, drag to restructure, import and export XMind and Markdown, export PNG/SVG/PDF. - [Password Generator](https://qilingtools.com/en/password): Free online random password generator: choose length, character sets and look-alike exclusions, generate several at once with a strength meter, all locally. - [QR Code Generator](https://qilingtools.com/en/qrcode): Free online QR code generator: turn URLs, text, Wi-Fi or contact cards into QR codes with custom size, colour and error correction. Crisp PNG or vector SVG. - [Word Counter](https://qilingtools.com/en/word-count): Free online word counter: live counts of characters with and without spaces, words, CJK characters, lines, paragraphs, sentences, bytes and reading time. - [Case Converter](https://qilingtools.com/en/case-convert): Free online case and naming converter: get UPPERCASE, lowercase, Title Case, camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE at once. - [Lorem Ipsum Generator](https://qilingtools.com/en/lorem): Free online Lorem Ipsum generator: classic Latin placeholder text or Chinese filler by paragraph, sentence or word, with one-click copy for mockups. - [Sort & Dedupe Text](https://qilingtools.com/en/text-sort): Free online text tool: sort lines alphabetically or by length, remove duplicate and empty lines, trim whitespace, optionally ignoring case. Runs locally. - [Sign & Stamp PDF](https://qilingtools.com/en/pdf/sign): Free online PDF signing tool: drop in a handwritten signature or company stamp, drag it into place on a page preview, adjust size and opacity, then export. - [Barcode Generator](https://qilingtools.com/en/barcode): Free online barcode generator: Code 128 with automatic code sets, EAN-13 with its check digit and Code 39. Adjust size, quiet zone and colours; SVG or PNG. - [BMI Calculator](https://qilingtools.com/en/bmi): Free online BMI calculator: height and weight give your body mass index, the WHO and Chinese categories, a healthy weight range, plus BMR and daily calories. - [Date Calculator](https://qilingtools.com/en/date-calc): Free online date calculator: days, weeks, months and workdays between two dates; add or subtract to find a date and its weekday; exact age and next birthday. - [Random Name Picker](https://qilingtools.com/en/random-picker): Free online random name picker: draw winners with no repeats across rounds, pick students at random, split people into balanced groups or shuffle a list. - [Text Cleaner](https://qilingtools.com/en/text-clean): Free online text cleaner: strip extra spaces and blank lines, rejoin lines broken by a PDF copy, convert full-width ↔ half-width and CJK ↔ Latin punctuation. - [Find and Replace](https://qilingtools.com/en/text-replace): Free online find and replace: several rules applied in order, plain text or regex, case and whole-word options, a live match count and $1 capture groups. - [Text to Speech](https://qilingtools.com/en/text-to-speech): Free text to speech: near-human AI voices run in your browser, unlimited, downloadable as WAV, in English and Chinese. System voices cover many more languages. - [Online Timer](https://qilingtools.com/en/timer): Free online timer: countdown with presets, alarm and screen flash; stopwatch with laps; Pomodoro 25/5 cycles. Big digits, accurate in background tabs. - [Time Zone Converter](https://qilingtools.com/en/timezone): Free online time zone converter and world clock: pick a time and see it in New York, London, Tokyo, Shanghai or any city, with UTC offsets and DST handled. - [Chart Maker](https://qilingtools.com/en/chart): Free online chart maker: paste data from Excel or CSV to build bar, line, area, pie, donut and scatter charts, then download a 2× PNG or an editable SVG. - [Chinese to Pinyin](https://qilingtools.com/en/pinyin): Free online Chinese to pinyin converter: tone marks, numbers or none, initials only, context-aware polyphones, surname readings and ruby annotation. - [Simplified ↔ Traditional Chinese](https://qilingtools.com/en/zh-convert): Free online Chinese converter powered by OpenCC: Simplified ↔ Traditional for Taiwan, Hong Kong or OpenCC standard, with optional Taiwan vocabulary. - [Signature Maker](https://qilingtools.com/en/image/signature): Free online e-signature tool: photograph a handwritten signature for a clean transparent PNG with paper and shadows removed, or draw one and export PNG or SVG. - [Chinese Lunar Calendar](https://qilingtools.com/en/calendar): Free Chinese lunar calendar for 1900–2100: lunar dates, zodiac, stem-branch years, the 24 solar terms with exact times, festivals and a lunar date converter. - [Morse Code Translator](https://qilingtools.com/en/morse): Free online Morse code translator: text to Morse and back, played as audio with adjustable WPM and tone, a flashing light, a WAV download, and space-bar keying. - [Online Notepad](https://qilingtools.com/en/notepad): Free online notepad that autosaves in your browser: several notes, search, rename, undo delete, word count, Markdown preview, TXT/MD export and focus mode. - [Typing Speed Test](https://qilingtools.com/en/typing-test): Free online typing test: WPM, CPM and accuracy over 30s, 60s, 120s or a full passage, with live error highlighting, a speed chart and personal bests. - [Spin the Wheel](https://qilingtools.com/en/wheel): Free online spinning wheel: add weighted options, spin with a tick sound, see the history, remove winners, use presets, and share a wheel by link. - [Days Until / Days Since](https://qilingtools.com/en/countdown): Free online days-until and days-since counter: add exams, holidays and anniversaries and see a live count to the second, with repeats and a share link. - [Emoji Picker](https://qilingtools.com/en/emoji): Free online emoji picker: 1,100+ emoji in nine groups, searchable in English and Chinese — click to copy, pick a skin tone, see code points and shortcodes. - [Flashcards](https://qilingtools.com/en/flashcards): Free online flashcards with SM-2 spaced repetition: grade each card Again, Hard, Good or Easy; several decks, CSV and Anki import, saved in your browser. - [Kanban Board](https://qilingtools.com/en/kanban): Free online Kanban board: several boards with custom columns, cards with labels, due dates and checklists, drag and drop or keyboard moves, autosaved locally. - [Split Bill](https://qilingtools.com/en/split-bill): Free online bill splitter for trips and dinners: add people and expenses, split equally, by share or by amount, and settle with the fewest transfers. - [Annotate PDF](https://qilingtools.com/en/pdf/annotate): Free online PDF annotator: highlight, draw, add shapes, arrows, sticky notes and text boxes, then save as editable annotations or flatten them. Runs locally. - [Invoice & Quote Generator](https://qilingtools.com/en/invoice): Make invoices, quotes, receipts and proforma invoices online: line items with discounts and tax, automatic totals, logo and signature, 3 templates, PDF. - [Password Strength Checker](https://qilingtools.com/en/password-checker): Test password strength privately in your browser: entropy and crack time, detects common passwords, keyboard walks, dates and l33t, optional breach check. - [Resume Builder](https://qilingtools.com/en/resume): Build a resume or CV online: photo, experience, education, skills and custom sections you can reorder, 4 templates, live A4 preview with page breaks, PDF. - [Word Cloud Generator](https://qilingtools.com/en/word-cloud): Free word cloud maker: paste text or open a file, word counts with stopword removal, editable frequency table, heart, star or image shapes, PNG and SVG. - [Create PDF Form](https://qilingtools.com/en/pdf/create-form): Make any PDF fillable: draw text fields, checkboxes, radio buttons, dropdowns, date and signature fields; set names, required flags and tab order. Free, local. - [Habit Tracker](https://qilingtools.com/en/habit-tracker): Free habit tracker: daily or weekly goals, one-tap check-ins, current and best streaks, monthly calendar, yearly heatmap, stats, notes and JSON/CSV export. - [Speech to Text](https://qilingtools.com/en/speech-to-text): Free online speech to text: talk into your mic for live transcription in 20+ languages with timestamps, auto punctuation, editing and TXT or SRT export. - [Teleprompter](https://qilingtools.com/en/teleprompter): Free online teleprompter: your script scrolls at your WPM pace. Set font size, spacing and colors, mirror for beam-splitter glass, count down, go full screen. - [Online Whiteboard](https://qilingtools.com/en/whiteboard): Free online whiteboard: infinite canvas, pressure-aware pen, highlighter, eraser, shapes, arrows, text and sticky notes, undo/redo, pages and PNG/SVG export. - [Calendar Maker](https://qilingtools.com/en/calendar-maker): Free printable calendar maker: a year on one page or a page per month, with holidays, week numbers, events, monthly photos and themes. Print or export PNG. - [Flowchart Maker](https://qilingtools.com/en/flowchart): Free flowchart maker: describe nodes and links in plain text (Mermaid flowchart syntax) for an auto-laid-out diagram with shapes and themes. SVG/PNG export. - [Gantt Chart Maker](https://qilingtools.com/en/gantt): Free online Gantt chart maker: tasks with dates or durations, progress, milestones and dependencies, working days, drag to reschedule, PNG/SVG/CSV export. - [Online Spreadsheet](https://qilingtools.com/en/sheet): Free online spreadsheet and CSV editor: SUM, AVERAGE and IF formulas with auto-recalc, sort, filter, find & replace, Excel copy-paste, CSV/TSV/JSON export. - [Screenshot Annotator](https://qilingtools.com/en/image/annotate): Free screenshot annotator: paste with Ctrl+V, add arrows, boxes, numbered steps, highlighter and text, pixelate or blur secrets, crop, copy or save PNG/JPG. - [Certificate Maker](https://qilingtools.com/en/certificate): Make award certificates in bulk: classic, gold, modern and simple templates, a pasted list of names, {name}/{award} placeholders, seal, PDF or PNG ZIP. - [Class Timetable Maker](https://qilingtools.com/en/timetable): Make a class timetable online: Mon–Fri to Mon–Sun, periods with times, auto colors, quick fill, merged double periods, A4 landscape print, PNG, CSV and JSON. - [Unit Price Calculator](https://qilingtools.com/en/unit-price): Compare products by unit price: per oz, lb, kg, L, item or sheet, with % off, spend-and-save, second-item discounts and buy-N-get-M deals. Finds the best value. - [WeChat Article Formatter](https://qilingtools.com/en/wechat-format): Turn Markdown into WeChat Official Account articles: 8 themes, code highlighting, tables, nested lists, links as footnotes, one-click copy that keeps styles. - [Business Card Maker](https://qilingtools.com/en/business-card): Design business cards: 9 front/back templates, US, EU, China and Japan sizes, logo, colors, vCard QR code, print-ready PDF with 3 mm bleed and crop marks. - [Handwriting Practice Sheet Maker](https://qilingtools.com/en/copybook): Make printable handwriting sheets: Chinese tian/mi grids, pinyin grids, manuscript paper, English four-line paper, tracing or model-and-trace, PDF or PNG. - [Chinese ID Number Validator](https://qilingtools.com/en/id-card): Validate Chinese ID numbers (GB 11643-1999): check digit, birth date, region, gender, age, zodiac; 15-to-18 upgrade; batch check with CSV. Runs locally. - [Envelope & Address Label Printer](https://qilingtools.com/en/label-print): Print envelopes (DL, C5, C6, US #10, Chinese with postcode boxes) and A4/Letter label sheets (L7160, L7163, L7651, 5160) from CSV with {field} templates. - [QR Code Art Generator](https://qilingtools.com/en/qr-art): Free styled QR code maker for URLs, Wi-Fi, vCards, email, SMS and maps: dot or diamond modules, custom eyes, gradients, logo, PNG/SVG/JPG and a scan check. - [Seating Chart Maker](https://qilingtools.com/en/seating-chart): Make classroom, U-shape, round-table or conference seating charts: seeded random, by height, boy–girl, keep-apart/together rules, locks, rotation, print. - [Batch File Renamer](https://qilingtools.com/en/batch-rename): Free bulk file renamer: find & replace with regex, prefixes, numbering, case, EXIF photo date, extensions. Live preview, conflict checks, ZIP or rename script. - [Bingo Card Generator](https://qilingtools.com/en/bingo): Make printable bingo cards: 75-ball B-I-N-G-O, UK 90-ball tickets or custom word and emoji bingo, all unique, 1–6 per page, with a call sheet and caller. - [Graph Paper Generator](https://qilingtools.com/en/graph-paper): Make printable paper: square grid, dot, isometric, hex, polar, log, engineering, music staff, guitar tab, Cornell notes, lined and calligraphy as vector PDF. - [Printable Planner Maker](https://qilingtools.com/en/planner): Printable planner pages: daily, weekly, monthly, year at a glance, habit tracker, to-do, meal plan, budget and reading log, with auto dates for a month or year. - [Word Search & Crossword Maker](https://qilingtools.com/en/word-puzzle): Make printable word search and crossword puzzles from your words and clues: diagonal and backwards words, compact numbered crosswords, answer keys, seeds. - [Duplicate Photo Finder](https://qilingtools.com/en/image/duplicates): Find duplicate and similar photos in your browser: SHA-256 for identical files, perceptual hashes for resized or recompressed copies; keep the best, export CSV. - [Decision Matrix](https://qilingtools.com/en/decision-matrix): Weighted decision matrix online: score options against criteria, set weights directly or by AHP pairwise comparison with CR, rank and test sensitivity. - [Expense Tracker](https://qilingtools.com/en/expense-tracker): Free private expense tracker: categories, accounts, tags, currencies, monthly budgets, pie, trend and heatmap reports, recurring bills, CSV import. Stays local. - [Markdown Slides](https://qilingtools.com/en/markdown-slides): Write slides in Markdown: --- splits slides, 9 themes, 16:9 or 4:3, code highlighting, columns, backgrounds, fragments, presenter view, PDF and HTML export. - [PDF Form Mail Merge](https://qilingtools.com/en/pdf/form-merge): Fill a PDF form from CSV rows: auto-matched fields, checkboxes, radios, dropdowns, CJK text, optional flattening, one PDF per row or combined; export form data. - [Email Signature Generator](https://qilingtools.com/en/email-signature): Create a professional HTML email signature: 8 templates, photo or logo, social icons, CTA banner and disclaimer, table-based for Gmail, Outlook and Apple Mail. - [Invitation & Greeting Card Maker](https://qilingtools.com/en/invitation): Make invitations and greeting cards for weddings, birthdays, baby showers, parties and holidays: 12 templates, QR codes, one card per guest, PNG or PDF. - [Text Analyzer](https://qilingtools.com/en/text-analyzer): Analyze text in depth: word and character frequency, n-grams, SEO keyword density, Flesch, Fog and SMOG scores, sentence lengths, MTLD and repeated phrases. - [Brain Tests](https://qilingtools.com/en/brain-tests): Free quick brain tests: reaction time, sequence, number, verbal and visual memory, aim trainer, chimp test, Stroop test and Schulte tables, with personal bests. - [Meeting Planner](https://qilingtools.com/en/meeting-planner): Find a meeting time across time zones: add cities and working hours, see overlaps on a 24-hour timeline, get best-time picks and export .ics or Google Calendar. - [Reading Speed Test](https://qilingtools.com/en/reading-speed): Test your reading speed: original English and Chinese passages at three levels, a comprehension quiz, effective WPM vs. average, plus an RSVP speed reader. - [Rename PDFs by Content](https://qilingtools.com/en/pdf/rename): Batch rename PDFs by content: put dates, invoice or order numbers, emails, totals, titles or labelled text into a name pattern; preview clashes. - [Letter & Document Templates](https://qilingtools.com/en/doc-templates): Free fill-in templates: leave request, receipt, IOU, employment verification, authorization and resignation letters, plus Chinese formats. Print, PDF or copy. - [Gift Ledger](https://qilingtools.com/en/gift-ledger): Free private gift ledger: log wedding, shower and birthday gifts received and given, see each person’s balance, get return-gift ideas and print a list. - [Shift Schedule Maker](https://qilingtools.com/en/shift-schedule): Free shift scheduler: set staff, shifts and daily headcount, then auto-build a fair roster that respects rest and weekly-off rules. Rotations, print, CSV. - [ZIP Compressor](https://qilingtools.com/en/zip): Free online ZIP tool: pack files or a whole folder into one zip, pick a compression level and optionally protect it with AES-256, all inside your browser. - [Unzip Online](https://qilingtools.com/en/unzip): Free online zip extractor: open a zip with nothing installed, browse and preview what is inside, extract only what you need, use a password, fix garbled names. - [ZIP Password](https://qilingtools.com/en/zip-password): Free online tool to password-protect a zip or strip the password from one you can open: AES-256 or ZipCrypto, with garbled filenames repaired on the way. - [RAR / 7Z Extractor](https://qilingtools.com/en/unarchive): Free online extractor for RAR, 7Z, TAR, TAR.GZ, TAR.XZ, TAR.BZ2, CAB, ISO and more: browse the contents, preview files and extract what you need without WinRAR. - [TAR Archiver](https://qilingtools.com/en/tar): Free online tar tool: pack files or a whole folder into .tar or .tar.gz with the folder structure intact, built in your browser and never uploaded. - [Split / Join Files](https://qilingtools.com/en/split-file): Free online file splitter: cut a big file into .001 .002 parts by size or count to fit an attachment limit, and join the parts back together. Runs locally. - [Excel Converter](https://qilingtools.com/en/excel-convert): Free online Excel converter: open an xlsx, read every worksheet and export it as CSV, TSV, JSON, a Markdown table or HTML. Date serial numbers become dates. - [Word Converter](https://qilingtools.com/en/word-convert): Free online Word converter: read headings, lists, tables, images and footnotes out of a docx and export Markdown, single-file HTML or plain text. - [PowerPoint Converter](https://qilingtools.com/en/ppt-convert): Free online PowerPoint converter: read each slide's title, bullet levels, tables, images and speaker notes out of a pptx and export Markdown, text or notes. - [TXT to EPUB](https://qilingtools.com/en/txt-to-epub): Free online TXT to EPUB converter: chapters are detected to build the table of contents, legacy encodings are repaired, and you can add a cover and author. - [EPUB Converter](https://qilingtools.com/en/epub-convert): Free online EPUB converter: read the whole book in reading order and export Markdown, plain text or a single-file HTML page, or print it to PDF. Parsed locally. - [EPUB Metadata Editor](https://qilingtools.com/en/epub-meta): Free online EPUB metadata editor: change the title, author, language, publisher, description and subjects, replace the cover and repack a valid EPUB. - [Peer-to-peer send](https://qilingtools.com/en/p2p): Free peer-to-peer file transfer: scan one QR code to pair a phone and a computer, then files go straight between them — no upload and no size limit. - [OFD viewer](https://qilingtools.com/en/ofd): Free online OFD viewer: open the .ofd files used by Chinese e-invoices and official documents, convert them to searchable PDF or PNG, and extract the text. - [China Phone Number Check](https://qilingtools.com/en/phone-check): Free checker for Chinese mobile numbers: validate the format, identify the carrier by prefix, flag MVNO, IoT and satellite ranges, and export them as CSV. - [ICS Calendar File](https://qilingtools.com/en/ics): Free online ICS generator: build .ics files with times, location, recurrence and alarms for Apple Calendar, Outlook or Google, or read an .ics someone sent you. - [Seal Extractor](https://qilingtools.com/en/image/seal): Free online seal extractor: lift a red or blue stamp off a scan into a transparent PNG, dropping paper, tint and specks. Solid colour, auto-trim, runs locally. ### Developer Tools - [JSON Formatter](https://qilingtools.com/en/json): Free online JSON formatter: beautify or minify, validate with the exact line and column of any error, browse a collapsible tree, sort keys and escape strings. - [Base64 Encode/Decode](https://qilingtools.com/en/base64): Free online Base64 encoder and decoder: UTF-8 safe, optional URL-safe variant, convert text to Base64 and back in real time. Processed locally, never uploaded. - [URL Encode/Decode](https://qilingtools.com/en/url-encode): Free online URL encoder and decoder with encodeURIComponent and encodeURI modes. Escapes Chinese, spaces and special characters. Real-time and local, no upload. - [JWT Decoder](https://qilingtools.com/en/jwt): Free online JWT decoder: decode the header and payload of a JSON Web Token, show expiry and issued-at times, all locally without uploading the token. - [Timestamp Converter](https://qilingtools.com/en/timestamp): Free online Unix timestamp converter: convert timestamps and dates, auto-detect seconds or milliseconds, and show local, UTC, ISO 8601 and relative time. - [Hash / Checksum](https://qilingtools.com/en/hash): Free online hash calculator: SHA-1, SHA-256, SHA-384 and SHA-512 of text or any file through the browser crypto API. Files never leave your device. - [UUID Generator](https://qilingtools.com/en/uuid): Free online UUID generator: create RFC 4122 UUID v4 in bulk with a cryptographic RNG. Options for uppercase, no hyphens and braces, with one-click copy. - [Base Converter](https://qilingtools.com/en/base-convert): Free online number base converter: convert between binary, octal, decimal, hexadecimal and any base 2–36. Uses BigInt for huge integers, computed locally. - [Regex Tester](https://qilingtools.com/en/regex): Free online regular expression tester: match and highlight as you type, list capture groups and support the g/i/m/s/u flags. Runs locally, nothing uploaded. - [Text Diff](https://qilingtools.com/en/text-diff): Free online text diff tool: compare two texts line by line, highlight added and removed lines, and optionally ignore case and trailing spaces. Runs locally. - [Color Converter](https://qilingtools.com/en/color): Free online color converter: convert between HEX, RGB and HSL with a built-in color picker and preview, one-click copy, computed locally in real time. - [HTML Entity Encode/Decode](https://qilingtools.com/en/html-entity): Free online HTML entity encoder and decoder: escape < > & " and more to entities or decode them back, with optional non-ASCII conversion. Runs locally. - [Cron Expression](https://qilingtools.com/en/cron): Free online cron tool: parse a 5-field cron (min hour dom mon dow), break down each field and predict the next 5 run times in your local zone. Computed locally. - [Markdown Preview](https://qilingtools.com/en/markdown): Free online Markdown previewer: render Markdown to a live web preview with GFM, tables and code blocks, copy the generated HTML. Runs locally, no upload. - [Chmod Calculator](https://qilingtools.com/en/chmod): Free online chmod calculator: tick read, write and execute for owner, group and others to convert octal (755) and symbolic (rwxr-xr-x), with setuid and sticky. - [Subnet Calculator](https://qilingtools.com/en/cidr): Free online IPv4 subnet calculator: enter 192.168.1.10/24 for the network, broadcast, host range and count, wildcard mask, binary view and a prefix table. - [CSV to JSON](https://qilingtools.com/en/csv-json): Free online CSV ⇄ JSON converter: handles quotes, commas and newlines inside fields, auto-detects the delimiter, with a header toggle and type conversion. - [HTTP Status Codes](https://qilingtools.com/en/http-status): Complete HTTP status code reference: every 1xx–5xx code with its name and a plain-language explanation, searchable by code, name or keyword. - [JSON to TypeScript](https://qilingtools.com/en/json-to-ts): Free online JSON to TypeScript converter: interfaces or types from JSON, nested objects split into named interfaces, optional fields inferred, Go structs too. - [Markdown Table Generator](https://qilingtools.com/en/markdown-table): Free online Markdown table generator: edit cells visually, add rows and columns, set per-column alignment, and import from Excel, CSV, TSV or Markdown. - [SQL Formatter](https://qilingtools.com/en/sql-format): Free online SQL formatter: beautify SELECT, JOIN, subqueries, CASE and WITH with clause line breaks and indentation, set keyword case, or minify to one line. - [Unicode Converter](https://qilingtools.com/en/unicode): Free online Unicode converter: text to and from \uXXXX, HTML entities, UTF-8 hex bytes, %XX and U+ code points, with correct emoji handling and auto-detection. - [URL Parser](https://qilingtools.com/en/url-parse): Free online URL parser: split a link into protocol, host, port, path and hash, edit decoded query parameters in a table, rebuild the URL live, export as JSON. - [User-Agent Parser](https://qilingtools.com/en/user-agent): Free online User-Agent parser: browser and version, rendering engine, OS, device type and model, and bot detection for Googlebot, Bingbot and GPTBot. - [Truth Table Generator](https://qilingtools.com/en/math/truth-table): Free online truth table generator: enter a Boolean or propositional expression for the full table, tautology check, canonical DNF/CNF and Quine–McCluskey. - [CSS Formatter](https://qilingtools.com/en/css-format): Free online CSS beautifier and minifier: one declaration per line, correct @media, nesting and url() handling, optional property sorting and a byte count. - [JSON Diff](https://qilingtools.com/en/json-diff): Free online JSON diff: compare two documents ignoring key order, see added, removed and changed paths with old and new values, and export an RFC 6902 patch. - [XML Formatter](https://qilingtools.com/en/xml-format): Free online XML formatter: beautify or minify XML, validate it with line and column errors, keep comments and CDATA, and convert XML to JSON and back. - [YAML to JSON Converter](https://qilingtools.com/en/yaml-json): Free online YAML and JSON converter: multi-document YAML, anchors, aliases and merge keys, errors with line and column, plus indent, sorting and folding. - [CSS Gradient Generator](https://qilingtools.com/en/css-gradient): Free online CSS gradient generator: build linear, radial and conic gradients visually with draggable stops, an angle dial and presets. Copy CSS or export PNG. - [CSS Box Shadow Generator](https://qilingtools.com/en/css-shadow): Free online CSS shadow generator for box-shadow and text-shadow: stack layers with offset, blur, spread and colour, start from presets, copy CSS or Tailwind. - [curl Converter](https://qilingtools.com/en/curl-convert): Free online curl converter: paste a curl command and get fetch, axios, Node, Python requests, Go, PHP or Java code, plus a parsed view of the request. - [Text Encryption & Decryption](https://qilingtools.com/en/encrypt): Free online text encryption: AES-256-GCM or CBC with a password (PBKDF2, OpenSSL-compatible output), raw key + IV mode, RSA-OAEP and HMAC signatures. - [JSONPath Tester](https://qilingtools.com/en/json-path): Free online JSONPath tester: query JSON with $.store.book[*], recursive .., slices and filters, listing every matching path and value, plus a cheat sheet. - [HTML Formatter](https://qilingtools.com/en/html-format): Free online HTML formatter: beautify or minify in one click, keep 
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