Two screenshots, two exports of a design, a photo before and after retouching: something changed, but where? This tool puts the two images in one place and lets you look at them five ways: side by side, with a slider that wipes between them, as a blend with adjustable opacity, as a map of pixel differences, and as image B with the changed areas outlined.
Both images stay in your browser. The tool reports exactly which pixels differ; it does not claim to understand what the difference means.
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Overview
About Image Compare / Diff
The views. Side by side shows A and B next to each other. Slider shows A on the left part and B on the right, divided at the slider position, which makes small shifts stand out. Opacity blend lays B over A with adjustable transparency. Pixel differences draws, for each pixel, how far the colours differ (amplified so small changes are visible), black meaning identical. Changed areas draws B with the differing pixels tinted red and the larger changed regions boxed.
The numbers. A pixel counts as different when its largest channel difference (red, green, blue or alpha) exceeds the tolerance you set; with tolerance 0 any change counts. The report gives the number and percentage of changed pixels, the largest single difference, and a table of the biggest changed regions found by joining neighbouring changed cells on a 16-pixel grid.
Different sizes. If the two images differ in size you choose how to compare: scale B to the size of A, or align the top-left corners (or centres) and compare the area they share. The report states which was used and shows each image\'s format, size in pixels and file size.
Mobile. Controls and results stack vertically on narrow screens, and wide results scroll inside their own frame instead of widening the page.
Compatibility
Supported Formats
JPEG, PNG and WebP images up to 30 MB, 12,000 pixels on a side and 40 megapixels each (decided by the content, not the name). Two images are needed. Animated images are compared by their first frame.
Guide
How to Use Image Compare / Diff
- Drop image A (before) and image B (after).
- Choose a view and move the slider or opacity control.
- Raise the tolerance to hide compression noise, or set it to 0 to see every change.
- Read the report and the changed-region table.
Highlights
Features
- Five views Side by side, slider, opacity blend, difference map and changed areas.
- Exact numbers Changed pixel count and percentage, largest difference and a table of changed regions.
- Size handling Scale B to A, or compare the shared area from the corner or centre.
- Format and size report Each image's format, pixel dimensions and file size.
- Private and mobile friendly Runs in your browser with a single-column layout on narrow screens.
Applications
Use Cases
- Checking what a design export changed between two versions
- Spotting a visual regression between two screenshots
- Seeing the effect of compression, resizing or a filter on a picture
- Finding what was retouched in a photo by comparing it with the original
- Confirming that two files that should be identical really are
Good to Know
Limitations
This compares pixels, not meaning. It cannot tell a real edit from re-compression noise, a colour-profile change, anti-aliasing or a one-pixel shift, and it does not recognise objects, text or faces. Use the tolerance to separate noise from changes, and your own eyes to judge them.
Scaling image B to the size of A introduces small differences of its own. Images of different shapes cannot be compared meaningfully without cropping first. Very large images use a lot of memory and can be slow on small devices.
This tool runs entirely in your browser — your file is never uploaded to our servers. See our Privacy Policy for full details.
Support
Frequently Asked Questions
Are my images uploaded?
No. Both images are drawn and compared in your browser. Nothing is sent to our server.
What does the tolerance do?
It is the largest colour difference (0-255) that is still treated as "no change". Raise it to ignore JPEG noise; set it to 0 to see every difference.
My images have different sizes. What happens?
Choose to scale B to A's size, or to align the corners or centres and compare the common area. The page tells you which was used.
Can it tell me what changed?
It shows where pixels differ and by how much. It does not understand what the pixels mean, so interpreting a difference is up to you.
Why do two identical-looking images show differences?
Usually compression, a colour profile, resampling or anti-aliasing. Raise the tolerance and look at the difference map: noise appears as faint speckle, real changes as solid areas.
Does it work on a phone?
Yes. The layout is single-column on narrow screens and the result scrolls in its own frame. Large images can be slow on small devices.
Keep Going
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