What if A and B have different sizes?

The diff is skipped and an inline banner tells you. Use the image resize tool to align dimensions and try again.

How should I pick the tolerance?

0 means exact match only. For JPEG-compressed images, start around 5–15 to suppress compression noise. For screenshot diffs, 1–3 is usually enough.

Diff-only vs. overlay?

Diff-only produces a PNG with a transparent background and only the highlight pixels — handy as a mask. Overlay dims image A under the diff so you can see the context of each change.

Can I compare animated GIFs or videos?

Only the first frame of a GIF is compared. For videos, export a still first (the video-frame-extract tool works well) and feed it in.

Is anything uploaded?

No. Everything runs in your browser using Canvas + getImageData.

Back to Image

Image difference — highlight pixel diffs between two images

Compare two images (JPEG / PNG / WebP / GIF) pixel-by-pixel on a canvas and produce a diff image that highlights only the changed pixels in your chosen color. Great for design QA, plagiarism checks, regression testing, or screenshot diffing. Tunable threshold lets you ignore near-identical pixels and shows the match percentage. Two display modes (diff only / overlay on top of the original). Everything runs in the browser — your images are never uploaded.

imagediff

How to use

Drop or pick the two images into the A and B slots. Their dimensions must match exactly. Pick a display mode (diff only / overlay on image A) and adjust the tolerance and highlight color. The diff image is recomputed automatically. Match percentage and changed pixel count appear in the summary. Click Download to save the result as PNG.

FAQ

What if A and B have different sizes?: The diff is skipped and an inline banner tells you. Use the image resize tool to align dimensions and try again.
How should I pick the tolerance?: 0 means exact match only. For JPEG-compressed images, start around 5–15 to suppress compression noise. For screenshot diffs, 1–3 is usually enough.
Diff-only vs. overlay?: Diff-only produces a PNG with a transparent background and only the highlight pixels — handy as a mask. Overlay dims image A under the diff so you can see the context of each change.
Can I compare animated GIFs or videos?: Only the first frame of a GIF is compared. For videos, export a still first (the video-frame-extract tool works well) and feed it in.
Is anything uploaded?: No. Everything runs in your browser using Canvas + getImageData.

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