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Image Difference Checker

Overlay two images and highlight their pixel-level differences. All processing stays in your browser.

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About Image Difference Checker

Overlay two images and highlight pixel-level changes in red. Images are processed entirely in your browser and are never uploaded to our server.

How to use

  1. 1.Select an Image A and Image B file.
  2. 2.Adjust the tolerance if needed and compare the images.
  3. 3.Review the difference percentage and download the difference PNG if needed.

Useful for

  • Comparing website screenshots
  • Reviewing before-and-after design changes
  • Checking image export quality

Verified examples and scope

These examples describe reproducible behavior in this tool. They are not a guarantee for inputs outside the documented scope.

Input or settingExpected resultCondition
Two identical 1×1 RGBA images, tolerance 00 changed pixels and 0% differenceAll four RGBA channels are identical.
1×1 images differing by 17 in red only, tolerance 161 changed pixel and 100% differenceA pixel changes when the maximum absolute channel delta exceeds tolerance.

Known limitations

  • Each JPEG, PNG, or WebP input is limited to 10 MiB and 4 megapixels.
  • Different dimensions are either stretched to the larger size or placed at original size from the top-left.

If the result is unexpected

  • For unexpected differences, use equal dimensions and formats, then verify tolerance and dimension handling.

How it works

For every pixel, the tool takes the maximum absolute delta across RGBA and compares it with a 0–255 tolerance.

Both images, filenames, and generated difference data are processed in the browser.

Input examples

  • Before-and-after website screenshots
  • Two exports made with different image settings

Notes and limitations

  • Use images with matching dimensions for exact pixel comparison.
  • Adjust tolerance to ignore minor JPEG compression or antialiasing differences.

Frequently asked questions

Are my images uploaded?

No. Loading, comparison, and difference-image generation all happen locally in your browser.

Can I compare images with different dimensions?

Yes. Both images are fitted to the larger comparison dimensions. For exact pixel comparison, images with matching dimensions are recommended.

What does tolerance do?

Tolerance ignores small color changes. Increase it when compression or antialiasing differences should not count as changes.