Alt text is the description a screen reader speaks when it reaches an image — and the text search engines read to understand it. Most sites either leave it empty or stuff it with keywords. Both waste one of the easiest wins on the web.
The one-sentence rule
Write what you would say if you were reading the page aloud to someone and reached the image. "A bar chart showing sales doubling between January and June" — not "chart", not "sales-chart-graph-data-analytics-2026.png".
Before and after
| Weak | Strong |
|---|---|
| "image1" | "Handwritten signature on a contract's final page" |
| "dog" | "Golden retriever catching a frisbee mid-jump" |
| "best free pdf compressor tool online free" | "Before/after file sizes: 8.4 MB reduced to 1.1 MB" |
The rules that matter
- Be specific, stay under ~125 characters. Screen readers may truncate longer descriptions.
- Skip "image of" / "picture of". The screen reader already announces it's an image.
- Decorative images get empty alt (
alt="") — not missing alt. Empty tells screen readers to skip; missing makes them read the filename aloud. - Text inside an image must be in the alt. If a banner says "50% off this week", the alt says it too.
- One natural keyword is fine if it genuinely describes the image; stuffing reads as spam to Google and as noise to a blind user.
Paste a page's HTML and get a scored report on meta tags — including missing alt attributes.
Open Meta Tag AnalyzerAlt text and image SEO
Google Images drives real traffic, and alt text is its primary ranking signal. The supporting cast matters too: a descriptive filename (golden-retriever-frisbee.jpg beats IMG_4032.jpg), a sensible display size, and a modern format so the page stays fast. Compressed, well-described images are one of the few optimizations that help accessibility, speed and rankings simultaneously.
The empty-alt decision
Ask: does this image carry information the surrounding text doesn't? A product photo — yes, describe it. A decorative gradient divider — no, alt="" and move on. When in doubt, describe it briefly; a slightly redundant description beats a silent gap.