Image Alt Text: Describing Pictures So AI Understands Them
To a machine, an image with no alt text is a blank space. Alt text is the short written description of what a picture shows. It was created for screen-reader users, and it does double duty for AI: it’s how your charts, product photos, and diagrams become part of what an AI can actually read and cite.
What good alt text looks like
Describe the content and its purpose — briefly and specifically.
- Vague:
alt="image"oralt="photo1.jpg"— useless. - Good:
alt="Bar chart: AI referral traffic up 40% from Q1 to Q2"— conveys the actual information. - Product:
alt="Red leather messenger bag, front view"rather thanalt="bag".
<img src="/chart.png" alt="Bar chart: AI referral traffic up 40% from Q1 to Q2">When to leave it empty
Purely decorative images — a background flourish, a divider line — should have an empty alt: alt="". That deliberately tells a machine “skip this, it carries no information,” which is different from a missing alt. Use empty alt for decoration; write real alt for anything that means something.
Why it’s worth it
Alt text serves two audiences at once: people using screen readers, and the AI deciding whether your page answers a question. The same handful of words helps both. One caution from search guidance: describe honestly — don’t stuff keywords into alt.
The bottom line
Give every meaningful image a short, specific alt that conveys its information; give decorative images alt="". It makes the visual parts of your page readable to AI and accessible to people. It’s one of the “be understandable” steps in our GEO overview.