A short text description attached to an image in a webpage's HTML, describing what the image shows — displayed if the image fails to load, read aloud by screen readers for accessibility, and used by search engines to understand image content.
Why it matters
Alt text serves two genuinely important, distinct purposes at once — accessibility for visually impaired users relying on screen readers, and search visibility, since search engines can't directly "see" an image and rely on alt text (along with surrounding context) to understand and index it.
In a sentence
"We audited alt text across the site and found a lot of images either missing it entirely or using unhelpful placeholder text like 'image1.jpg.'"
Related terms
- Often confused with: Caption (alt text is typically not visible to a sighted user browsing normally; a caption is visible text displayed alongside an image for every visitor, serving a different, more editorial purpose).
- Synonyms: Alt attribute, image description.