What Is Alt Text?
Alt text is a written description attached to an image for accessibility and search engines. How to write it well, and a real example.
Alt text is a short written description attached to an image in the HTML (alt="..."), read aloud by screen readers and used by search engines to understand what an image shows since they can’t literally “see” it. It also displays if the image itself fails to load.
Why alt text matters
Good alt text improves accessibility for visually impaired users, a real functional need, not a checkbox, and can help images surface in Google Image search, a traffic source many sites ignore entirely despite it being genuinely free additional visibility. It’s also a legal consideration in some jurisdictions under accessibility standards like WCAG. Skipping alt text, or filling it with keyword-stuffed nonsense instead of an actual description, fails on both fronts at once: a screen reader user gets no useful information, and search engines get a signal that reads as manipulative rather than descriptive.
How to write good alt text
- Describe what’s actually in the image, specifically enough to convey the same information a sighted user would get at a glance.
- Keep it concise, generally under 125 characters, since some screen readers truncate longer alt text.
- Skip “image of” or “picture of.” Screen readers already announce it’s an image; adding that phrase wastes space.
- Include the relevant keyword only if it genuinely describes the image, never force a keyword into an inaccurate description.
- Use an empty
alt=""for purely decorative images, so screen readers skip them rather than announcing irrelevant filler.
Common alt text mistakes
- Leaving it blank on meaningful images. This is the single most common failure and directly harms accessibility.
- Keyword stuffing. Cramming multiple keyword variations into one description reads poorly to screen readers and looks manipulative to search engines.
- Using the filename instead. “IMG_4821.jpg” tells neither a screen reader user nor a search engine anything useful.
- Writing alt text for purely decorative images. Adds unnecessary noise for screen reader users; use an empty
alt=""instead.
Good vs. weak alt text
| Weak alt text | Stronger alternative |
|---|---|
| “image1.jpg” | “Golden retriever hiking on a forest trail” |
| “dog, dogs, puppy, pet, animal, cute dog” | “Golden retriever puppy playing in a backyard” |
| Blank on a meaningful photo | A specific, concise description of what’s shown |
Real example
For example, a photo of a golden retriever on a hiking trail might have alt text reading “golden retriever hiking on a forest trail,” rather than being left blank or labeled “image1.jpg,” giving both a screen reader user and Google Image search a clear, accurate description to work with.
Alt text and AI search
Alt text remains one of the clearest signals available for helping AI systems, and multimodal search features, understand and correctly describe an image’s content, since many AI models still rely partly on this same accessibility metadata alongside visual analysis. Well-written alt text is one of the few SEO practices that genuinely serves accessibility, traditional search, and AI interpretation simultaneously with no tradeoff between them.
FAQ
Do all images need alt text?
Meaningful, content-relevant images do. Purely decorative images (background textures, spacers) should use an empty alt="" rather than a forced description.
Is alt text a ranking factor?
It’s a relevance signal, particularly for Google Image search, rather than a major factor for standard web ranking, but it contributes to overall page context and accessibility compliance.
How long should alt text be?
Generally under 125 characters, concise but specific enough to convey the image’s actual content and relevance.
What’s the difference between alt text and a caption?
Alt text is invisible metadata read by screen readers and search engines; a caption is visible text displayed alongside the image for all visitors. They can say similar things but serve different, non-interchangeable purposes.
Related terms
Alt text isn’t an SEO trick, it’s accessibility that happens to help SEO too. Write it for the person who can’t see the image first, the ranking benefit follows.