Automated accessibility tests miss issues on 71% of top sites by checking only one browser state

A developer tested 36 well-known websites — including GitHub, Wikipedia, BBC, and GOV.UK — across seven distinct browser states, such as dark mode, narrow viewport, and reduced motion. Standard automated accessibility pipelines typically test only a single default state, missing conditions that real users encounter daily. The experiment found that 24 of 34 stable sites had accessibility issues in non-default states that the baseline scan never detected, totalling 296 deduplicated findings. Narrow viewport and dark colour scheme were the biggest culprits, affecting 26 and 25 sites respectively, with colour-contrast violations appearing most frequently. Six sites — including W3C, MDN, and GOV.UK — were clean across all seven states, most of them organisations with formal accessibility responsibilities.