Image Difference Checker

Compare two images in your browser. View an Original and a Comparison side by side, with an overlay slider or as a pixel difference image, set a threshold, see the changed-pixel count and percentage, and download the difference as PNG.

Image Runs client-side Free to use

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About the Image Difference Checker

Image Difference Checker compares two images pixel by pixel without uploading them. Add an Original and a Comparison image; the tool shows each file’s format, dimensions and size, then lets you view them side by side, as an overlay with a slider that reveals the Comparison over the Original, or as a pixel difference image where changed pixels are shown in red over a faded copy of the Original. It reports how many pixels changed and what percentage of the image that is.

A threshold from 0 to 255 controls how big a difference must be before a pixel counts as changed, so you can ignore small compression or resizing noise or reveal subtle edits. Images of different sizes can be compared by resizing the Comparison to match the Original, and the tool says clearly when it has done so. Results depend on how the files were saved: JPG and WebP compression, resizing and colour profiles all create differences, so this is a visual aid, not proof that an image was or was not edited.

How to use

Choose the Original image and the Comparison image.
If the sizes differ, turn on resizing to match.
Pick Side by side, Overlay slider or Pixel difference image.
Adjust the threshold and read the changed-pixel count and percentage.
Download the difference image as PNG.

Key features

Clearly labelled Original and Comparison inputs with dimensions.
Side-by-side, overlay slider and pixel difference views.
Threshold control from 0 to 255.
Changed-pixel count, percentage and largest difference found.
Optional resize-to-match with a clear disclosure.
Difference PNG download, progress for large images and Reset.

Best practices

Compare lossless PNG files when you need precise results.
Raise the threshold to ignore JPG compression noise.
Use images of the same size where possible — resizing adds differences.
Use the overlay slider to check alignment and small shifts.
Treat the result as a guide, not as evidence of tampering.

Benefits

Spot visual regressions in screenshots and designs.
Check before-and-after edits quickly.
Clear numbers alongside visual views.
Private: both images stay on your device.

Frequently asked questions

What counts as a changed pixel?

A pixel whose red, green, blue or alpha value differs by more than the threshold between the two images. At threshold 0 any difference counts.

Why are there differences in images that look identical?

JPG and WebP compression, re-saving, resizing, colour-profile conversion and browser decoding can all change pixel values slightly. Raise the threshold to ignore small differences.

Can I compare images of different sizes?

Yes, by turning on resize-to-match, which scales the Comparison to the Original’s dimensions. Resampling creates small differences of its own, especially at edges, and the tool tells you when it has resized.

Can this prove that an image was edited?

No. It is a visual comparison aid, not a forensic tool. A difference does not prove an edit, and no difference does not prove two files are the same.

What does the difference image show?

Changed pixels in red over a faded grey copy of the Original, so you can see where changes are. You can download it as a PNG.

Is there a size limit?

Each file can be up to 50 MB, and comparisons are limited to 20 megapixels so your browser stays responsive. Large comparisons show progress and can be stopped with Reset.

Are my images uploaded anywhere?

No. Files are opened and processed by JavaScript running in your browser tab. Nothing is sent to a server, and images, SVG code and results are not saved in browser storage — they are cleared when you press Reset or close the page.