Alt text
A text description of an image, intended for anyone who can't see it. Read aloud by screen readers, shown when the image fails to load and indexed by search engines.
The rule most often missed: a decorative image should have an empty alt="", not a missing attribute. Empty means "skip this one", while a missing attribute makes the screen reader read out the filename — and IMG_20260729_final2.jpg helps nobody. Describe the function rather than the appearance: for a button what it does, for a chart what it shows, for a photo what is relevant in context. If the image contains text, include the text. The requirement lives in WCAG 1.1.1 and therefore in public sector accessibility law. Mastodon, Bluesky and LinkedIn have dedicated alt text fields, and filling them in has become an established norm in parts of the fediverse.