Alt Text

Alt text is a written description of an image embedded in a web page's code, used by screen readers to convey the image to people who cannot see it and by search engines to understand what the image depicts. It does not normally appear on the visible page, though browsers display it in place of an image that fails to load. In short, alt text is the textual stand-in for a picture, serving accessibility and search at the same time.

Mechanically, alt text lives in the alt attribute of an image tag in HTML. When a screen reader encounters the image, it reads the alt text aloud, allowing a visually impaired user to understand the content and purpose of the picture within the flow of the page. Search engines, which cannot truly see images, rely on the alt text along with the file name and surrounding context to interpret and index the image, which is why it influences whether an image appears in image search. Good alt text is specific and concise: it describes what the image shows and, when relevant, its function, without padding. Decorative images that carry no meaning are handled differently, typically with an empty alt attribute so screen readers can skip them rather than announce clutter.

The term is short for "alternative text," drawn from the HTML alt attribute that was introduced so that images could carry a text alternative. The attribute has existed since the early days of web markup, created precisely so that a page would remain meaningful when an image could not be seen or loaded, whether because of a disability, a slow connection, or a broken file.

For a business, alt text matters for two reasons that reinforce each other. First, it is a core accessibility practice, helping people who use assistive technology understand your content and, in many jurisdictions, supporting compliance with accessibility standards and reducing legal risk. Second, it contributes to search visibility: descriptive alt text helps your images rank in image search and adds relevant context that can strengthen the page overall. A retailer whose product photos carry accurate alt text is more discoverable and more usable, which serves both customers and search performance.

There are important nuances. A common mistake is keyword stuffing the alt attribute, cramming in search terms that do not describe the image; this harms the experience for screen reader users and offers no real search benefit. The opposite error, leaving alt text blank on meaningful images, wastes an accessibility and search opportunity and can leave assistive-technology users lost. Writing overly long, rambling descriptions is also unhelpful, since screen readers will read every word. Another subtlety is knowing when an image is purely decorative and should have an empty alt attribute rather than a forced description. It helps to remember that alt text primarily serves the human using a screen reader; if the description would genuinely convey the image to someone who cannot see it, it will usually serve search well too. The practical approach is to describe each meaningful image accurately and briefly, in natural language, and to mark decorative images so they can be skipped.