What Is Alt Text, and Why Does It Actually Matter?

Alt text (short for "alternative text") is a short description attached to an image in your page's HTML, using the alt attribute. It doesn't show up visually in most browsers — you only see it if the image fails to load, or if you're using a screen reader, which reads it aloud in place of the image.

That second use case is the important one. For someone who is blind or has low vision, alt text is often the only way to know what's in an image at all — a product photo, a chart, a screenshot, a person in a blog post header. Without it, a screen reader either skips the image entirely or reads out the filename, which is rarely useful ("IMG_4821.jpg" tells you nothing).

Alt text also matters for search. Search engines can't "see" an image any more than a screen reader can — they rely on surrounding text, including alt attributes, to understand what an image shows and when it's relevant to a search query. Product pages with accurate, descriptive alt text on their photos tend to show up more often in image search results, which is real, measurable traffic for e-commerce and content sites alike.

There's a third, quieter benefit: alt text is a fallback for everyone. Slow connections, ad blockers that strip images, and broken image links all mean a visual-only page occasionally shows nothing where an image should be. Good alt text means the page still makes sense.

The catch is that writing genuinely accurate alt text for hundreds or thousands of images is slow, tedious work — which is exactly the gap AI vision models are suited to close, since they can actually look at an image and describe what's there instead of guessing from a filename.