Image Diff Checker
Upload two images and see a pixel-accurate visual diff between them, with perceptual YIQ comparison and anti-aliasing-aware highlighting — 100% local in your browser.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
Shipped a CSS tweak and want to know exactly what moved? Comparing two screenshots for a QA visual-regression check? Wondering what actually changed between two exported versions of the same photo? Scrolling back and forth between two images and squinting for differences is slow and unreliable — this tool overlays the two and shows you every changed pixel in one image.
The comparison is real pixel-diffing math, the same family of algorithm used by tools like pixelmatch: every pixel of both images is converted from RGB into YIQ color space (Y = luma, I and Q = the NTSC chrominance axes), and the Euclidean distance between the two YIQ points is computed. That distance is compared against a threshold set by the sensitivity slider — raise the sensitivity to catch subtle color shifts, lower it to ignore compression noise and care only about obvious changes.
A naive per-pixel comparison would light up every anti-aliased edge as "different" even when nothing meaningful changed, because smoothing shifts a handful of border pixels by a few shades. This tool runs a real anti-aliasing heuristic on both images: a pixel is only treated as a genuine difference if it does NOT sit inside a smoothing gradient — concretely, if its own 3x3 neighborhood in either source image does not already contain both a lighter and a darker pixel than itself, which is the fingerprint of an AA-smoothed edge rather than actual content.
Upload Image A and Image B, adjust the sensitivity if needed and press Execute. You get an exact percentage of pixels that differ plus a diff image with every real change highlighted in bright magenta over a dimmed version of the original — download it and attach it straight to your bug report or QA notes. Both images must share the same dimensions; if they don't, the tool tells you plainly instead of silently cropping or stretching one of them. Nothing leaves your browser at any point.
Example. Two images of equal size are compared in YIQ, and pixels whose delta exceeds the sensitivity threshold are painted magenta.
Limit. The two pictures must have the same pixel width and height, or the comparison stops with a dimension error.