Pixel diff
Compares two images pixel-by-pixel and shows exactly where they differ.
Drop two images and the tool compares them pixel-by-pixel, highlighting mismatches in red over the semi-transparent original. Shows the count and percentage of differing pixels; when sizes differ, it compares the common subregion. Adjustable threshold (Euclidean RGB distance) and output mode: highlight in red, black-and-white mask only, or side-by-side A | B | mask. Output is a PNG plus a short text report, packed in a ZIP. Useful for designers (what changed between two mockup versions), QA (screenshot tests) and re-encoding checks (what was lost). Runs in the browser.