# Free Online Developer Tools: JSON Formatter, CSV to JSON, JSON to TypeScript, SQL Formatter, Subnet Calculator

> 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.

- URL: https://qilingtools.com/en/dev
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

## Tools (93)

- [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 <pre> and <textarea> intact, format embedded CSS and JSON-LD, with a sandboxed live preview.
- [JWT Generator & Signer](https://qilingtools.com/en/jwt-generate): Free online JWT generator: edit the header and payload, sign with HS, RS, PS or ES 256/384/512, make RSA / EC key pairs, and verify with exp/nbf checks locally.
- [Keycode Finder](https://qilingtools.com/en/keycode): Free online JavaScript key event viewer: press a key to see event.key, code, keyCode, location and modifiers, with an on-screen keyboard and a reference table.
- [Mock Data Generator](https://qilingtools.com/en/mock-data): Free online mock data generator: define fields and generate up to 10,000 rows of fake names, emails, addresses, dates and IDs, exported as JSON, CSV or SQL.
- [WebSocket Tester](https://qilingtools.com/en/websocket-test): Free online WebSocket client: connect to ws:// or wss://, send text, JSON or binary messages, read a filterable log, auto-reconnect, plus an SSE tester.
- [.gitignore Generator](https://qilingtools.com/en/gitignore): Free .gitignore generator: combine 40 templates (Node, Python, Java, Go, Rust, Unity, macOS, VS Code…), dedupe, add custom rules, test which paths git ignores.
- [JavaScript Formatter](https://qilingtools.com/en/js-format): Free online JavaScript formatter: beautify or minify JS, TypeScript, JSX and JSON with 2/4-space or tab indent and line width. Handles regex, templates, ASI.
- [JSON Schema Generator & Validator](https://qilingtools.com/en/json-schema): Generate a draft 2020-12 or draft-07 JSON Schema from sample JSON (types, required, nesting, formats) and validate JSON with JSON Pointer error paths. Free.
- [Meta Tag Generator](https://qilingtools.com/en/meta-tags): Free SEO meta tag generator & checker: title, description, canonical, robots, Open Graph, Twitter cards, hreflang, JSON-LD, with Google and social previews.
- [docker run ↔ Compose Converter](https://qilingtools.com/en/docker-convert): Convert docker run to docker-compose.yml and back: ports, volumes, env, networks, healthchecks, limits, logging and GPUs, plus warnings for unsupported flags.
- [HTTP Request Tester](https://qilingtools.com/en/http-request): Free online HTTP client: send GET, POST, PUT or DELETE with params, headers, JSON, form or file bodies and auth, then inspect status, timing, headers and body.
- [Nginx Config Generator](https://qilingtools.com/en/nginx-config): Generate Nginx configs for static sites, SPAs, reverse proxies, WebSocket and PHP-FPM with HTTPS, HTTP/2, gzip, caching, security headers and rate limits.
- [String Escape / Unescape](https://qilingtools.com/en/string-escape): Escape or unescape strings for JSON, JavaScript, Java, C#, C, Go, Python, SQL, bash, regex, CSV, XML and URL, with every changed character highlighted.
- [SVG Optimizer](https://qilingtools.com/en/svg-optimize): Optimize SVGs online: strip editor data and unused defs, compact path data, compare previews side by side, batch ZIP download, Data URI and React JSX export.
- [Color Contrast Checker](https://qilingtools.com/en/color-contrast): Check color contrast: WCAG 2.x ratio and APCA Lc, AA/AAA pass or fail for text and UI, nearest passing color, color-blindness preview and palette matrix.
- [Multi-Encoding Converter](https://qilingtools.com/en/encoding): Convert text, hex or files to Base32, Base58Check, Base62, Base36, Ascii85, Z85, binary, Quoted-Printable, Punycode and more, with auto-detection on decode.
- [Regex Visualizer](https://qilingtools.com/en/regex-visualizer): Visualize JavaScript regexes as railroad diagrams with a plain-language breakdown of groups, quantifiers, classes and lookarounds. Export SVG or PNG.
- [Semver Tools](https://qilingtools.com/en/semver): Semver tools: validate SemVer 2.0.0, compare and sort versions, bump like npm version, and test npm ranges (^, ~, x-ranges, ||) with plain explanations.
- [Bcrypt Generator & Checker](https://qilingtools.com/en/bcrypt): Generate and verify password hashes online: bcrypt (cost 4–14, $2a/$2b/$2y), Argon2id, scrypt and PBKDF2, auto-detecting PHP, Django, Flask and passlib formats.
- [SSL Certificate Decoder](https://qilingtools.com/en/cert-decoder): Decode SSL/TLS certificates online: subject, issuer, days to expiry, SANs, key usage, OCSP/CRL, SCTs and SHA-256 fingerprints, with chain and signature checks.
- [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.
- [HTML to Markdown Converter](https://qilingtools.com/en/html-markdown): Convert HTML to Markdown and back: headings, nested lists, task lists, GFM tables, code blocks, links and images. Paste rich text from web pages or Docs.
- [TOTP Generator](https://qilingtools.com/en/totp): Generate and verify TOTP / HOTP 2FA codes from a Base32 secret or otpauth:// URI. SHA1/256/512, 6–8 digits, custom period, countdown, new secrets and QR codes.
- [Config File Converter](https://qilingtools.com/en/config-convert): Convert config files between JSON, YAML, TOML, INI, .env and Java .properties. Auto-detects the format, full TOML 1.0 support, errors with line numbers.
- [CSS clip-path Generator](https://qilingtools.com/en/css-clip-path): Visual CSS clip-path maker: drag polygon points or use circle, ellipse and rounded inset. 25 presets (arrow, star, speech bubble) previewed on your image.
- [Flexbox & Grid Playground](https://qilingtools.com/en/flex-grid): Interactive Flexbox and CSS Grid playground: tweak container and item properties live, drag to name grid-template-areas, and copy CSS, HTML or Tailwind classes.
- [robots.txt & Sitemap Generator](https://qilingtools.com/en/robots-sitemap): Build robots.txt (block GPTBot, ClaudeBot and other AI bots in one click), test URLs with Google’s rules, and generate or validate sitemap.xml.
- [Tailwind Color Palette Generator](https://qilingtools.com/en/tailwind-palette): Turn a brand color into a Tailwind-style 50–950 scale on the default palette’s OKLCH curve, with contrast badges and v3, v4, CSS, SCSS and JSON export.
- [Htpasswd Generator](https://qilingtools.com/en/htpasswd): Generate .htpasswd entries with bcrypt, APR1-MD5, SHA-512/256 crypt or {SHA}, merge into existing files, verify passwords and get nginx / .htaccess config.
- [IPv6 Calculator](https://qilingtools.com/en/ipv6): Free IPv6 toolkit: RFC 5952 compress/expand, prefix ranges, paged subnetting, address types (Teredo, 6to4, NAT64), EUI-64, ip6.arpa and random ULA.
- [JSON to SQL Converter](https://qilingtools.com/en/json-to-sql): Convert JSON arrays or CSV to SQL: inferred types and primary key, CREATE TABLE, batched INSERT and UPSERT for MySQL, PostgreSQL, SQLite, SQL Server, Oracle.
- [OpenAPI Viewer](https://qilingtools.com/en/openapi-viewer): View OpenAPI 3.x and Swagger 2.0 (JSON/YAML) online: tag-grouped endpoints, search, $ref schema trees, example JSON, curl/fetch snippets and HTML export.
- [ASCII Table Generator](https://qilingtools.com/en/text-table): Turn CSV, spreadsheet cells or Markdown into text tables: ASCII, Unicode boxes, Markdown, reST, Org-mode, MySQL style, HTML or LaTeX, CJK-aligned.
- [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.
- [Protobuf, MessagePack, CBOR & BSON Decoder](https://qilingtools.com/en/binary-decoder): Decode raw Protobuf without a schema or with a pasted .proto, plus MessagePack, CBOR and BSON. Tree + JSON views with byte-offset highlighting.
- [Hex Viewer](https://qilingtools.com/en/hex-viewer): View any file as hex + ASCII: go to offsets, search bytes or text, decode values, detect 60+ file types, parse PNG/ZIP/PDF/ELF/PE headers and diff files.
- [HTTP Security Headers Checker](https://qilingtools.com/en/security-headers): Paste raw HTTP response headers to get an A+ to F grade with checks for HSTS, CSP, X-Frame-Options, cookies, CORS and more, plus fixes and a CSP builder.
- [Sorting Algorithm Visualizer](https://qilingtools.com/en/sorting-visualizer): Watch 14 sorting algorithms animate: bubble, insertion, shell, merge, quick, heap, counting, radix, bucket and Timsort, with counters, step mode and races.
- [XPath & CSS Selector Tester](https://qilingtools.com/en/xpath-tester): Test XPath 1.0 and CSS selectors on XML or HTML: live highlighting, namespace prefixes, function results and shortest unique selectors for any clicked node.
- [Kubernetes YAML Generator](https://qilingtools.com/en/k8s-yaml): Generate Kubernetes manifests: Deployment/StatefulSet, Service, Ingress, ConfigMap, Secret, HPA, PVC and CronJob, with validation and docker run/compose import.
- [Open Source License Picker](https://qilingtools.com/en/license-picker): Answer a few questions to choose an open source license, compare 15 licenses side by side, and generate a filled-in LICENSE, SPDX headers and manifest fields.
- [SSH Key Generator](https://qilingtools.com/en/ssh-keygen): Generate SSH key pairs in your browser: Ed25519, RSA 2048/3072/4096 or ECDSA, with OpenSSH keys, passphrases, PKCS#8, fingerprints and randomart.
- [systemd Unit Generator](https://qilingtools.com/en/systemd-unit): Generate systemd .service and .timer files with restart, dependencies and hardening explained; convert cron to OnCalendar, preview next runs, lint units.
- [CSS Animation Generator](https://qilingtools.com/en/css-animation): Build CSS @keyframes animations visually: 18 presets, a keyframe timeline, cubic-bezier and steps() easing, live preview, and copy CSS or Tailwind config.
- [GraphQL Formatter](https://qilingtools.com/en/graphql-format): Format, minify and validate GraphQL queries and SDL: syntax errors with line and column, unused variables and fragments, curl and fetch snippets, a type graph.
- [Color Palette Generator](https://qilingtools.com/en/palette-generator): Press space for new color palettes, lock favorites, use OKLCH harmonies or image colors, check contrast and color blindness, export CSS, Tailwind, ASE.
- [SVG Wave & Shape Generator](https://qilingtools.com/en/svg-shapes): Generate SVG decorations: layered waves, random blobs, dot, hex and topographic patterns, layered peaks; gradients and seeds; export SVG, PNG, CSS or React.
- [SQL on CSV](https://qilingtools.com/en/csv-sql): Run SQL on CSV, TSV and JSON files in your browser: type inference, WHERE, GROUP BY, aggregates, JOINs, CASE, subqueries and functions; export CSV or JSON.
- [Invisible Character Detector](https://qilingtools.com/en/invisible-chars): Detect and remove zero-width characters, bidi controls (Trojan Source), non-breaking spaces, soft hyphens, control chars, homoglyphs and full-width letters.
- [JSON Graph Visualizer](https://qilingtools.com/en/json-graph): Turn JSON, YAML or CSV into a node graph: objects and arrays as cards linked by edges, with zoom, pan, collapse, search, JSONPath and PNG/SVG export.
- [File Checksum](https://qilingtools.com/en/checksum): Free online checksum tool: compute MD5, SHA-1, SHA-256 and CRC32 for several files at once, compare against a published value and handle multi-GB files.
- [SQLite Browser](https://qilingtools.com/en/sqlite): Free online SQLite browser: inspect tables, row counts and indexes, run real SQL in a genuine SQLite engine, export CSV / JSON or download the new .sqlite.
- [MIME types](https://qilingtools.com/en/mime-types): Free MIME type lookup: search 80+ common formats by extension or type, copy the Content-Type with one click, with notes on charset and download headers.
- [Port numbers](https://qilingtools.com/en/port-numbers): Free port number lookup: search 60+ common ports by number, service or purpose, see which must never face the internet, and find what is using one locally.
- [Git commands](https://qilingtools.com/en/git-commands): Free Git cheat sheet: 60+ commands grouped by what you want to do — undo, branch, rebase, remotes, history, stash, cleanup — with copy and danger warnings.
- [Commit message](https://qilingtools.com/en/commit-message): Free Conventional Commits generator: pick a type, fill in the summary and get a correct header, BREAKING CHANGE footer and a ready-to-paste git commit command.
- [.editorconfig](https://qilingtools.com/en/editorconfig): Free .editorconfig generator: choose indentation, line endings, charset and trailing-space rules, start from a project preset, and get the exceptions added.
- [Bitwise Calculator](https://qilingtools.com/en/bitwise): Free online bitwise calculator: AND, OR, XOR, NOT, shifts and rotates at 8, 16, 32 or 64 bits, with two's complement reading, clickable bits, hex and decimal.
- [ASCII Table](https://qilingtools.com/en/ascii-table): Free online ASCII table: codes 0-127 in decimal, hex, octal, binary and escape form, every control character explained, Latin-1 128-255 and a code point lookup.