Image alt text

Image alt text is the `alt` attribute on the `<img>` tag. Text description of an image for search engines, visually impaired users (via screen reader), and image load failures.

Why it matters

1. SEO — Google indexes images and shows them in Image Search. Alt is the main signal for what's in the image. 2. Accessibility — screen reader users "hear" the alt text. 3. Fallback — when image can't load, users see alt text instead. 4. GEO/AI — AI systems (especially multimodal) use alt to understand image context.

Good alt

• •Descriptive — tells what's in the image
• •Concise — 5-15 words optimal
• •Contains keyword — when appropriate, without stuffing
• •Contextual — accounts for page context

Examples

❌ Bad: `<img src="seo.jpg" alt="seo">` ❌ Bad: `<img src="audit.jpg" alt="seo audit buy order london cheap">` (spam) ✅ Good: `<img src="audit.jpg" alt="Screenshot of SEO audit dashboard in Google Search Console showing 90-day traffic graph">`

When alt isn't needed

Decorative images (backgrounds, dividers, meaningless icons) should have `alt=""` (empty). Tells screen readers "skip this".

<img src="divider.svg" alt="" role="presentation">

Top mistakes

1. Missing alt — critical accessibility and SEO issue 2. alt with filename — `alt="IMG_4521.jpg"` useless 3. alt keyword spam — Google demotes the page 4. Long alt (>150 chars) — use `figcaption` for descriptions 5. Same alt for all images — reduces relevance

How to check

Lighthouse → Accessibility → "Image elements do not have [alt] attributes". Screaming Frog → Images tab → Missing Alt Text.