Alt Text
Alt text is the written description you attach to an image so it can be understood when the image cannot be seen. It serves screen-reader users first, gives search engines context second, and shows up if the image fails to load.
Alt text gets treated like an SEO afterthought, and that is exactly backwards. Its first job is accessibility: a person using a screen reader hears your alt text in place of the image. Write it for that person, and the SEO benefit follows naturally, because a description that helps a human is also a description that helps a search engine understand the picture. Flip your thinking on this and you will never write a lazy alt attribute again. There is also a reputational angle worth naming, because accessibility is increasingly an expectation rather than a nice-to-have, and missing alt text is one of the most common and most visible gaps on the web. Doing it well signals that you build for everyone, which is the kind of detail that quietly separates serious sites from sloppy ones.
Write alt text for the person who cannot see the image, and the search benefit comes along for the ride.
Why alt text matters
- Accessibility: screen readers announce it so the content makes sense to everyone
- Image SEO: it gives engines context and helps you appear in image search
- Resilience: it displays when an image fails to load or is blocked by the connection
- Relevance: it reinforces what a page is about when used honestly and specifically
- 1Describe what the image shows, plainly and specifically.
- 2Keep it concise; one clear sentence usually does it.
- 3Skip 'image of' or 'picture of'; the screen reader already says it is an image.
- 4Include a keyword only if it genuinely fits the picture.
- 5Leave alt empty for purely decorative images so screen readers can skip them.
- 6Match the description to the image's job: a link image describes the destination.
Example
For a photo of a search results page, weak alt is 'screenshot.' Strong alt is 'Google results page showing a title tag and meta description for an SEO guide.' The strong version actually tells someone what they are looking at, which is the whole point. If a sighted person would learn something from the image, your alt text should pass that same information along to someone who cannot see it, no more and no less.
warningWATCH OUT
Do not stuff keywords into alt text. 'best cheap running shoes buy running shoes online running shoe deals' helps nobody, annoys screen-reader users, and can read as spam. Describe the image, full stop.
The decorative-versus-informative call is the one people get wrong most often. A photo that carries meaning, a product shot, a chart, a diagram, a screenshot, needs alt text that conveys that meaning. A purely decorative flourish, a background texture, a divider line, a stock image that adds nothing, should get an empty alt attribute so a screen reader skips right past it instead of reading 'decorative swirl graphic number four' to someone trying to follow your content. Knowing which is which is most of the skill, and the test is simple: if you removed the image, would the reader lose any information? If yes, describe it. If no, let it be empty.
| Image type | Alt text approach |
|---|---|
| Informative photo | Describe the subject and relevant detail |
| Chart or diagram | Summarize the data point or takeaway |
| Decorative only | Use empty alt so it is skipped |
| Image as a link | Describe where the link goes |
targetBottom line
Alt text is the cheapest accessibility win you have, and it quietly strengthens your on-page SEO at the same time. Write it like you are describing the image to someone over the phone, and you will get it right almost every time.
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