Screenshot Diffing: Pixel-Level Comparison Techniques

Screenshot diffing compares two images of the same page to detect visual changes. The four main approaches are pixel-by-pixel comparison (fast, brittle), perceptual hashing (fast, misses subtle changes), structural similarity index (models human perception, best balance), and AI-based diffing (handles dynamic content, expensive). The right choice depends on your tolerance for false positives and your budget. The Core Problem You have two screenshots: one from before a code change, one from after