Alt Text

Alt text, short for alternative text, is the written description you attach to an image in HTML using the image element's alt attribute. Its first and oldest purpose is accessibility. People who are blind or have low vision use screen readers — software that reads a page aloud — and when the reader reaches an image, it speaks the alt text. Without it, the reader announces "image" or reads the file name, which tells the listener nothing. Good alt text describes the picture in plain words so that someone who cannot see it still understands what it conveys and why it is there. The text also appears on screen if an image fails to load, and it gives search engines, which cannot truly interpret a picture, a reliable description of what the image shows.

Because it does three jobs at once, alt text is one of the small, high-leverage details of building a good page. The accessibility purpose comes first and is, in many places, a legal expectation rather than a nicety — public-sector and large commercial sites are frequently required to make images perceivable to assistive technology. The search benefit follows from the same writing: clear, accurate descriptions help images surface in image search and add a little context to the page's overall relevance. Crucially, these goals do not conflict. Writing alt text well for a blind visitor is, almost always, writing it well for a search engine too, because both want an honest, specific account of what the image actually depicts.

The skill in alt text is describing the image accurately for its context, not narrating every pixel. Ask what the image communicates on this particular page. A photo of a red leather handbag on a product page might read "red leather tote bag with gold buckle," because the color and detail matter to a shopper. The same photo in a blog post about sustainable materials might emphasize something else. Keep descriptions concise — a short, specific phrase usually beats a long sentence — and skip openers like "image of" or "photo of," since the screen reader already announces that it is an image. The test is simple: read your alt text aloud with your eyes closed and ask whether you would understand the picture from the words alone.

Two errors sit at opposite extremes. The first is keyword stuffing — cramming the alt attribute with search terms that do not describe the image — which makes the page hostile to screen-reader users and is treated by search engines as spam, the very behavior the attribute was never meant to carry. The second is leaving alt text off images that need it, which silences them for assistive technology and offers search engines nothing. There is a legitimate middle case, though: purely decorative images that add no information — a divider line, a background flourish — should carry an empty alt attribute (alt=""), which deliberately tells a screen reader to skip them. Empty is not the same as missing. An empty alt is a considered choice to omit a decoration; a missing alt is an oversight.

Write alt text for the person who cannot see the image, and the search benefit will follow. Describe the content and function of each meaningful image in plain, specific language, sized to the context — what does this picture need to convey here? Mention a relevant keyword only when it genuinely belongs in the description, never bolted on. For images that are also links or buttons, the alt text should describe the destination or action, not just the picture, because that is what a screen-reader user needs to act. For charts and infographics, state the takeaway rather than the label, since "chart" helps no one. And mark truly decorative images with an empty alt attribute so assistive technology passes over them cleanly.

The failure modes are easy to spot once you look. Missing alt attributes leave images mute for screen readers and blank to search. File-name alt text — "IMG_4821.jpg" — describes nothing. Generic placeholders like "image" or "picture" are no better. Keyword-stuffed alt text harms accessibility and risks a spam judgment. And over-describing decorative graphics clutters the audio experience with noise a listener does not need. The discipline is steady: describe each meaningful image accurately and briefly, write for the listener first, keep keywords honest, and use an empty alt for decoration. Do that and the same text serves the blind visitor, the broken-image fallback, and the search crawler all at once.

Alt text — alternative text — is the written description of an image in HTML, read aloud by screen readers, shown when an image fails to load, and used by search engines to understand the picture.

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