GlossaryVisual regression testing
Visual regression testing
Definition
Automatically comparing screenshots of a site before and after a change, to catch unintended visual differences.
Visual regression testing guards against accidental change: it renders pages before and after a deploy and diffs the pixels, flagging anything that moved. It answers "did we break how it looked yesterday?", which makes it a developer tool first.
It differs from design comparison, which checks the page against the design file rather than against a previous screenshot. Regression testing catches what changed unexpectedly; design comparison catches what never matched the design in the first place. Mature teams end up wanting both.
