What is Image Alt Text?
Image alt text is a short written description of an image, set on the HTML alt attribute (for example, alt="Black leather Chelsea boot, side profile"). It is invisible on the page but read aloud by screen readers, shown when an image fails to load, and parsed by AI engines and search crawlers. WCAG 2.1 Success Criterion 1.1.1 requires a text alternative for all non-text content — meaning every meaningful image needs alt text.
AI engines like ChatGPT, Perplexity, and Google AI Overviews increasingly cite multi-modal content. Most do not run vision on every image — they read the alt text, captions, and surrounding HTML to decide what an image shows and whether to cite the page. Pages where text, images, and structured data all reinforce the same topic get cited far more often. This metric is part of the Technical Foundation pillar in your GEO-Score.
Why Alt Text Matters for AI Search
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Alt text is one of the few signals that pulls triple duty: it is a legal accessibility requirement, a confirmed image search ranking factor, and the primary text input AI engines use to interpret your visuals. Skipping it costs you on all three fronts simultaneously.