How to Write Image Alt Text for SEO and Accessibility

Alt text, short for alternative text, is a written description attached to an image. Most visitors never see it, but it does important work behind the scenes for accessibility and for search.

Writing good alt text takes seconds per image and benefits everyone, from a customer using a screen reader to Google trying to understand your page.

Who alt text helps

For people who use screen readers, alt text is read aloud so they understand what an image shows. Without it, those visitors miss out, and in the UK accessible websites are increasingly expected.

Alt text also acts as a fallback if an image fails to load, and it gives search engines context about the picture, which can help your images and pages appear in results.

How to write it well

Describe what the image actually shows, plainly and concisely. "Stone cottage with a thatched roof in a Norfolk village" is far more useful than "image1" or a stuffed list of keywords.

Keep it natural and relevant. If a keyword fits the description honestly, include it, but never cram keywords in just for SEO. The description should make sense if read aloud.

When to leave it blank

Not every image needs alt text. Purely decorative images, such as a background pattern or a divider line, can have empty alt text so screen readers skip them rather than reading out noise.

The rule of thumb: if the image carries meaning, describe it. If it is purely decorative, leave the alt text empty. A web designer or your content system makes adding alt text straightforward.

Common alt text mistakes and how to fix them

Leaving alt text empty (alt="") or using the filename (alt="IMG_4523.jpg") are both useless for accessibility and SEO. Keyword stuffing — alt="web design norwich, website design norwich, web design company norwich" — is treated as spam by search engines. The correct approach is simply to describe what the image shows, accurately and briefly.

Decorative images — dividers, background textures, purely aesthetic elements — should have empty alt text to tell screen readers to skip them. Only images that carry information need descriptions. Running your site through a free accessibility checker such as WAVE identifies which images are missing alt text or have poor descriptions that need updating.