Alt text

A textual description of non-text content (primarily images) provided via the HTML alt attribute, read by screen readers and displayed when images cannot be loaded. Required by WCAG Success Criterion 1.1.1 (Level A), alt text should convey the same information or function as the visual content in context. Crucially, effective alt text is context-dependent: the same image requires different descriptions depending on its purpose on the page — a person's photo might need their name on a staff page, their clothing on a fashion site, or their action on a news article. Alt text should be concise (typically under 150 characters), describe purpose rather than appearance when the image is functional, and use an empty alt attribute (alt="") for purely decorative images. AI-generated alt text from vision-to-language models is increasingly available but requires webpage context to produce relevant descriptions and carries the risk of hallucination.