Compare two photos pixel by pixel, see how many changed, and download a red difference map that shows where they differ.
Image A — before
Image B — after
Both files are compared in this tab. Nothing is uploaded.
Choose two images to compare.
A changed-pixel count, a similarity percentage and a red difference map appear here.
The overlay is composed over image A. Red marks pixels whose colour (or transparency, when enabled) differs by at least the threshold. Images of different sizes are aligned at their top-left corner, because there is no reliable way to align two arbitrary photos.
Your file is never sent to a server. It is read and processed by your own browser, and the results are not stored.
Each pixel is compared channel by channel. The largest absolute difference among red, green, blue and optionally alpha decides whether it counts. The tool then reports how many pixels changed, the percentage over the compared area, and a bounding box around every change.
The overlay marks changed pixels in red and leaves everything else transparent. Composing it over image A produces a map you can read without switching between views.
A threshold of zero is exact: any difference in the encoded pixels counts. That is right for comparing a PNG against its edited copy, and noisy for comparing two JPEGs that went through different encoders.
A threshold around 8 ignores small quantisation differences while still catching a moved object, a colour change or a removed element. The right value depends on how the files were produced, so the tool exposes the number instead of hiding it.
No. Compare Two Images runs in your browser, and the file is read there rather than sent to a server for processing. Our host still sees ordinary page-request metadata, which is described on the privacy page.
Yes, Compare Two Images is free, with no paid tier, no account, and no watermark added to your output. The limits are technical rather than commercial: file size, page count and supported formats are listed on this page.
Compare Two Images supports .jpg, .jpeg, .png, .webp files up to 25MB directly in your browser.
They are aligned at their top-left corner and only the overlapping area is compared. The page says so explicitly and takes the percentage over the pixels that were actually compared, rather than pretending the missing area is identical or changed.
A pixel counts as changed only when a colour channel differs by at least the threshold. Zero counts any difference; a value around 8 tolerates the small errors introduced by JPEG re-encoding while still catching real edits.
When the pair is small enough, yes. Above roughly 8 megapixels the tool compares a proportionally scaled copy so two decoded bitmaps cannot exhaust a phone tab. The page reports the scale it used, and single-pixel differences below that scale may not appear.