ByteScope

Image Pixel Diff

Compare two images pixel by pixel — diff, blend, swipe, onion skin and blink.

Your files never leave your browser — all processing is local.

Drop two images to compare

A then B · click to browse · paste (Ctrl+V) anywhere on this page

About this tool

This is an image diff online tool for anyone who needs to compare two images pixel by pixel — designers checking a redline against a build, developers verifying a screenshot regression, or photographers spotting edits. Drop or paste image A and image B and the tool highlights exactly what changed, backed by a mature pixel-comparison engine with anti-aliasing detection so lossy-compression noise doesn't drown out real differences. A tolerance slider, per-channel difference amplification and automatic bounding boxes turn "these look different" into precise, measurable numbers.

Existing tools in this niche are surprisingly weak — most upload your files and give you a single, fixed comparison view. This one does five comparison modes locally in your browser (diff highlight, difference blend, swipe, onion skin and blink), never uploads a thing, and reports the changed-pixel count, percentage, maximum channel delta and the number of changed regions. It's the fast, private way to find the difference between images — mismatched sizes are handled too, by padding or scaling before the comparison runs.

Frequently asked questions

What comparison modes does this image diff tool offer?
Five, and you can switch between them instantly on the same pair: Diff highlight paints changed pixels in orange over a dimmed base; Difference blend shows the amplified |A−B| value image; Swipe drags a divider between the two images; Onion skin cross-fades B over A with an opacity slider; and Blink alternates A and B about twice a second. Most online tools give you one mode — comparing two images pixel by pixel is easier when you can flip between all five.
How do I compare two images that have different dimensions?
When the two images aren't the same size the tool warns you and offers two ways to reconcile them before diffing: 'Align top-left' pads the smaller image with transparency so both share a canvas, and 'Scale B to A' resamples the second image to the first image's dimensions. Pick whichever matches what you're checking.
What does the tolerance slider do?
Tolerance (0–255) sets how different two pixels must be before they count as a change. Raise it to ignore the tiny color shifts that lossy JPEG or WebP compression introduces, so you only see real differences. The tool also detects anti-aliased edges and can ignore them, which further cuts false positives when you want to find the difference between images that were re-encoded.
Are my images uploaded to a server?
No. All decoding and comparison run entirely in your browser inside a Web Worker — your images never leave your device, there is no upload step and no file-size limit beyond your machine's memory. You can even use the page offline once it has loaded.
Can I see where the changes are and export the result?
Yes. The stats panel reports the number and percentage of different pixels, the maximum per-channel delta, and how many separate regions changed. Turn on 'outline changed regions' to draw bounding boxes over the differences, and use 'Download diff.png' to save the current view as a PNG.
What's the difference between diff highlight and difference blend?
Diff highlight is a yes/no view: each pixel is either changed (orange) or not, controlled by the tolerance threshold. Difference blend is a continuous view: it shows |A−B| per channel multiplied by a gain factor, so faint, sub-threshold differences (gradients, compression artifacts, watermarks) become visible when you turn the gain up.

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