pixelmatch

pixelmatch is a small and fast JavaScript library for pixel-level image comparison, originally created to compare screenshots in tests. It returns the number of different pixels and can write a diff image highlighting them.

It detects anti-aliased pixels so that they are not reported as differences, and measures colour differences perceptually, with a configurable threshold. It has no dependencies, works on raw typed arrays of image data, and runs in Node.js and in browsers; a command-line interface and an official C++ port are also available. It is used as the comparison engine of several visual testing tools.

pixelmatch is developed by Mapbox and is free and open source under the ISC licence.