Compare PNG Images
Free PNG diff with no upload. Compare two PNG images pixel by pixel, alpha-aware and lossless, with adjustable tolerance and grouped differences.
Files never leave your browser.
Drop two PNGs to spot pixel-level differences. Alpha channels are preserved, so transparent pixels compare correctly. Use the tolerance slider to ignore tiny variations.
About PNG Diff
Compares two PNG images pixel by pixel in your browser. PNG is lossless, so two exports of the same artwork give the same pixels. Only a real edit shows as a difference, and the alpha channel is part of the compare.
How to use
- Drop or pick the left PNG. This page accepts PNG files only.
- Drop or pick the right PNG. A colour-coded mask marks every pixel that changed.
- Keep Color tolerance at 0 for an exact compare. Raise it only when one side was saved through a lossy format.
What this tool doesn't handle
- Both images need the same size. Turn on auto-scale for a mismatch, and fine-tune scale and offset in the alignment workspace. Resampling adds a little noise.
- Only the pixels are compared. PNG metadata chunks, the colour profile and the compression level are not read.
Frequently asked questions
Do my files ever leave my browser?
No. Every comparison runs locally in your browser. Nothing you paste, drop, or load is uploaded to a server; the tool keeps working even if you go offline after the page loads.
Is this tool free to use?
Yes. All DiffResolver tools are free, with no account, sign-up, or installation. Because processing happens on your device, there are no server-imposed usage limits.
Does the compare respect PNG transparency?
Yes. The alpha channel is read with the colour channels. A pixel that changes only in opacity counts as a difference, and pixels that are fully transparent on both sides count as equal.
Is a PNG compare exact?
Yes, at tolerance 0. PNG is lossless, so the same artwork gives the same pixels whatever the compression level. Because two clean exports differ in few pixels, the tool leaves the automatic tolerance at 0.
Can I compare an indexed PNG with a truecolour PNG?
Yes. Both files are decoded to RGBA before the compare, so the bit depth and the palette do not matter. A colour that the palette rounds still shows as a difference.
Is there a file size limit?
No server limit applies, because nothing is uploaded. The memory of your device sets the practical limit. Above 10 MB for text, 40 MB for images, 100 MB for documents, or 500 MB for archives, the tool warns you that the work can be slow, but it never blocks the file.
Does this tool work offline?
Yes. The browser keeps a copy of the tool after the first visit, so a page you opened before still works without a network. You can also install DiffResolver as an app from the browser menu. Installation stays optional; the site works the same in a normal tab.
Where is my data stored?
Your files are stored nowhere. They stay in the memory of the page and are gone when you close the tab. Only what you save yourself stays in this browser: a snapshot, your tool options, and your theme. To remove it, open Settings and select Clear all local data.