I pointed my UI-auditing tool at three sites it had never seen. All seven bugs it found were its own.

The line at the bottom of the report said: Records with automated findings: 8/4 Eight out of four. More screens with findings than screens. I wrote this tool. It measures web UIs — contrast ratios against the real composited background, touch targets under 44px, controls that something else is painting over, text clipped by its own container. It...