Alt text is a written description of an image, read aloud by screen readers and shown if the image fails to load — it serves both accessibility and (secondarily) SEO purposes.
Writing good alt text
- Describe what’s actually relevant about the image in context, not a generic label
- Keep it concise — typically under 125 characters is a reasonable target for screen reader compatibility
- Don’t start with "image of" or "picture of" — screen readers already announce it as an image
- Purely decorative images (that add no informational value) should have empty alt text (
alt=""), not be skipped entirely, so screen readers correctly skip over them
FAQ
Should alt text be stuffed with keywords for SEO?
No — keyword-stuffed alt text reads poorly to actual screen reader users and can be seen as a manipulative SEO practice; write for the person who can’t see the image first.