Farah Nasser

Automated checks find perhaps a third of real problems; the rest need a human reading the page. It is a ratio of relative luminance with a threshold that depends on rendered size and weight, so a large heading and a body sentence can use different thresholds for the same pair of colours. What a tool cannot tell you is what the text sits on, so a ratio computed against white is meaningless on a dark background or over a photograph. Alt text is the area where advice conflicts most. An informative image needs a description. A decorative one needs an empty alt attribute so a screen reader skips it, and omitting the attribute does not achieve that. A link whose text already says where it goes should not have its destination repeated in the alt text, because a screen reader reads both and the listener hears it twice. ARIA is the largest source of harm. It changes what assistive technology announces, it is frequently applied without need to something already announced sensibly, and a wrong role is worse than no role because it replaces correct behaviour with incorrect behaviour. The first rule of ARIA is not to use it where a native element exists. Keyboard operability is the check I would keep if I could keep only one. If a control cannot be reached or operated by keyboard, it does not exist for a large number of users. Focus order is the other check that costs nothing: tab through the page and confirm the order matches the visual order, which it often does not once something has been positioned absolutely.