Screenshot Comparison Algorithms: A Visual Testing Guide
· 21 min read
Pixelmatch, the diff engine behind Playwright's toHaveScreenshot(), processes a 1440×900 desktop screenshot in roughly 28 ms using YIQ NTSC color-distance math from Kotsarenko & Ramos (2010). SSIM costs about 85 ms on the same image. ODiff finishes the same job 8× faster than pixelmatch (ODiff README). Choosing between them is what separates a useful visual suite from a noise machine.