# Video Compare - Synced Playback, Slider Wipe, PSNR and SSIM

> Compare two videos in sync: side by side, slider wipe, difference or flicker, frame stepping, per-frame PSNR / SSIM graphs and labeled MP4 export.

- URL: https://qilingtools.com/en/video/compare
- Category: Video Tools (https://qilingtools.com/en/video)
- Tags: [Video](https://qilingtools.com/en/tags/video), [Photo Editing](https://qilingtools.com/en/tags/photo)
- Last updated: 2026-10-26
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

How much quality did compression, transcoding, denoising or a color grade really cost? Load the before and after videos and see for yourself. Both play in sync with A as the master, in four views: side by side, slider wipe (drag the divider back and forth), difference (frames subtracted pixel by pixel and amplified 2–16× so blocking and color shifts jump out) and flicker (A and B alternate at your chosen interval, which makes subtle changes easy to spot). Scroll to zoom and drag to pan with both sides locked together, down to individual pixels; step frame by frame, and use an offset to line up clips whose starts don’t match. For objective numbers, FFmpeg’s psnr and ssim filters compute PSNR and SSIM for every frame, with averages, minimums and the worst frame, plus a per-frame graph you can click to jump to that moment. Finally, export both videos stacked side by side or top and bottom as an MP4 with labels drawn by the browser, so any language renders correctly. Everything stays on your device.

## How to use

1. Add two videos: the first is A (original), the second is B (processed)
2. Play them in sync side by side, with the slider, difference or flicker view; set an offset or zoom in as needed
3. Compute PSNR / SSIM for objective metrics, or export a side-by-side or stacked comparison video

## Features

- Synchronized playback with frame stepping
- Side by side, slider wipe, difference and flicker views
- Zoom and pan locked across both videos
- Offset to align clips with different starts
- Per-frame PSNR / SSIM graph and worst-frame finder
- hstack / vstack export with labels

## FAQ

### How do I read PSNR and SSIM?

PSNR is in dB, and higher means closer to the original: above 40 dB is usually invisible, 30–40 dB shows slight loss and below 30 dB the loss is obvious. SSIM runs from 0 to 1, where values above 0.98 typically look identical. Identical videos give an infinite PSNR and an SSIM of 1.

### Can I compare videos with different resolutions or lengths?

Yes. The preview draws B at A’s size, and metrics scale B to A’s resolution before comparing each frame; with different lengths only the overlapping part is compared. Scaling itself adds a little difference, so keep resolutions equal when judging encoder quality.

### The two videos don’t start at the same moment. What should I do?

Enter an offset in seconds under Offset of B vs A: positive if B has extra lead-in, negative if it starts later, and use ±1f to nudge one frame at a time. Flicker or difference view makes alignment easy — when it’s right the image stops jumping. The offset applies to metrics and export too.

### Why is the difference view almost black?

Black means the two frames are nearly identical, which is what good encoding looks like. Raise Amplify difference to 8× or 16× to reveal blocking, ringing around edges and lost shadow detail; for color grades the difference concentrates where colors changed most.

## Related 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.