Compare Images
Compare two images with a slider, side by side, onion skin or a pixel difference heatmap, with percent changed and PSNR.
Free, no uploads, no sign-up. Runs 100% in your browser.
How Compare Images works
Both images are decoded locally and compared pixel by pixel using a perceptual colour distance (YIQ), the same idea used by visual regression tools. You get the share of changed pixels, the PSNR score, and a highlight or heatmap image you can download.
Input: JPG, PNG, WEBP, AVIF, TIFF, PSD, HEIC. Output: PNG.
How to use Compare Images
- Add the first and second image.
- Switch between slider, side by side, onion skin and difference.
- Adjust the threshold to ignore tiny changes such as compression noise.
Tips
- If the sizes differ, choose how to align them: stretch, top left or centre.
- A PSNR above 40 dB means the images look the same to most people.
Compare Images FAQ
- Is my file uploaded?
- No. Everything runs in this browser tab on your own device. Engines are downloaded once and cached, but your files never leave your computer.
- Are my files uploaded?
- No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.
- Is it free? Are there limits or watermarks?
- Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.
- Does it work offline?
- Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.
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- Image Converter: Convert JPG, PNG, WEBP, AVIF, BMP, GIF and ICO in bulk.
- Image Resizer: Resize to exact pixels, percentages or social presets.