How different are these two, really?
Scores how alike two versions of a picture are and shows a map of where they differ, amplified enough to see.
- Add
- Adjust
- Make
- Keep
How to use this tool
- Add your files — drag them onto the page or choose them. They stay on your device.
- Add the two files — the original and the re-saved copy, two encodes, two candidates.
- The comparison table lines up dimensions, duration, codecs, size and metadata differences side by side, and tells you whether they are pixel-identical.
- Press “Process files” and download the results, individually or as one ZIP.
About this tool
Scores how alike two versions of a picture are and shows a map of where they differ, amplified enough to see. Neither file is uploaded. Everything is analysed and produced on your own device — nothing is uploaded anywhere, and you can verify it: the tools keep working even offline.
Privacy & limitations
This compares two files' properties and bytes; it does not yet compute a perceptual similarity score between two different-looking images.
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Frequently asked questions
How do I tell if a compressed image lost quality?
Compare it against the original and measure rather than guess. SSIM tracks what people actually notice: above about 0.99 the difference is invisible outside a pixel-by-pixel comparison, and by 0.95 you can find it if you know where to look.
Why do the two images need the same dimensions?
Because overlaying different shapes compares the geometry rather than the encoding. If one has been resized or cropped, the score would be measuring your own decision, so it declines to give one instead of reporting a meaningless number.
Why is the difference map so bright?
It is amplified about six times. The real differences between a good compression and its original are a handful of values per channel, which is invisible on screen, so the map shows the shape of the error rather than its true intensity.