Accessible description

Every control gets two strings from the browser, and they have different jobs. The accessible name identifies it: “Delete project”. The accessible description elaborates: “This cannot be undone”. The name is announced immediately, with the role; the description follows, usually after a short pause, and only when the reader has arrived at the control. Keeping them apart is what stops a button from being called “Delete project this cannot be undone”, which is what happens when a hint is folded into the label.

The description has its own computation order, and it is short. aria-describedby wins, taking the text content of every element it points at, in the order the ids are listed. aria-description comes next, for a string with no element to point at. The title attribute is last, which is the only reason a stray title sometimes shows up as description in an inspector. There is no fallback beyond that, so a hint rendered next to a field and joined to nothing is a hint no screen reader user ever hears, however clearly it reads on screen.

When a description is announced is out of your hands, which is the practical constraint. Screen readers differ on verbosity settings, on whether they repeat descriptions in browse mode, and on how much of a long one they will speak before moving on. Anything essential to completing a task belongs in the name, the label, or the visible copy, and the description carries what is genuinely supplementary: a format hint on a field, a consequence on a destructive button, the error text that has just appeared. Point aria-describedby at the helper text and the error message you already render rather than writing the sentence twice, and let the association drop when the message does.

It is worth noting what this is not. Name, role, value is the audit of a control’s obligations, and the description is not one of them: a control with a perfect description and no name is still broken, and the fix is a name, not more description. title as the sole description is the weakest arrangement of the lot, because it appears on hover only, which excludes touch and keyboard entirely.