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  3. Image Diff Comparator
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Image Diff Comparator

Compare two images pixel-by-pixel. Multiple comparison modes: side-by-side, overlay, difference highlighting, onion skin, and slider. Perfect for visual regression testing.

Compare two images and highlight the differences between them. Upload a before and after version, and the tool overlays a diff visualization showing exactly what changed. Useful for QA, regression testing, or verifying design changes.

Runs in your browser and files never uploadedMore image processingJump to full guide

Initializing in your browser…

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Image Diff Comparator: a worked example

A visual regression test failed and you need to see exactly which pixels changed between two screenshots.

Input

baseline.png vs current.png
Image Diff Comparator produces

Result

0.7% pixels differ, highlighted cluster around the moved button

A pixel-level diff with a tolerance threshold isolates real changes from noise and visualises them, so a regression is localised in seconds instead of by squinting at two tabs. The percentage gives a pass/fail signal for CI-style checks.

What is Image Diff Comparator?

Compare two images and highlight the differences between them. Upload a before and after version, and the tool overlays a diff visualization showing exactly what changed. Useful for QA, regression testing, or verifying design changes.

How to use

  1. 1Upload two images to compare
  2. 2View the diff overlay highlighting changed pixels
  3. 3Adjust sensitivity to control what counts as a difference
  4. 4Toggle between overlay, side-by-side, and slider views

Key features

  • Pixel-level difference detection
  • Multiple comparison modes (overlay, side-by-side, slider)
  • Adjustable sensitivity threshold
  • Highlighted diff areas

Tips & best practices

  • For UI regression testing, capture screenshots at the same viewport size and zoom level for the most accurate comparison.

Common use cases

  • Visual regression testing

    Compare screenshots before and after code changes to catch unintended visual differences.

  • Design review

    Verify that a design revision changed only what was intended.

  • Photo editing comparison

    See exactly what changed between two versions of an edited photo.

Frequently asked questions

Do the images need to be the same size?

For accurate pixel comparison, yes. If sizes differ, the tool may resize one to match, but results are best with identically sized images.

What does the sensitivity slider do?

It sets how much a pixel must change before it is flagged as different. Higher sensitivity catches subtle changes; lower sensitivity ignores minor variations.

Private by design

Images are decoded, edited, and exported entirely inside this browser tab. No originals, exports, or metadata are uploaded.