Alt Text

Definition

Alt text (short for "alternative text") is the textual description of an image, specified in the `alt` attribute of an `<img>` tag. It serves three audiences: screen readers for visually impaired users, search engines that cannot visually interpret images, and AI models that need a textual representation of what an image shows.

Good alt text describes the content and function of the image as concisely as possible. It should describe what a sighted user would gain from seeing the image, not what the image literally depicts at the pixel level. Decorative images (dividers, spacers, pure aesthetic graphics) should have empty alt attributes (`alt=""`) to tell screen readers to skip them.

Why It Matters

Alt text is the single most important accessibility element on a web page. Over 97 percent of home pages have at least one image without alt text, according to the WebAIM Million report. Missing alt text is both an accessibility failure (WCAG 2.1 Level A violation) and a lost SEO opportunity.

For GEO, alt text has become more important, not less. Modern AI models absolutely read alt text when evaluating a page, because they often cannot or do not run vision models during retrieval. If your image contains a key stat, a product screenshot, or a chart, the LLM may never see the pixels, but it will read the alt text. Treating alt as "the text representation of the image's informational value" is the correct frame.

How Acta AI Handles This

Examples

Alt text should describe what the image communicates, not what the image file is called:

<!-- Bad: empty or missing alt on an informational image -->
<img src="chart-1.png">
<img src="chart-1.png" alt="chart">
<img src="chart-1.png" alt="chart-1.png">

<!-- Bad: keyword-stuffed -->
<img src="chart-1.png"
     alt="seo chart seo stats seo data 2026 seo">

<!-- Good: describes the information -->
<img src="chart-1.png"
     alt="Line chart showing organic traffic
          growth from 12K to 84K monthly visits
          between Jan 2024 and Mar 2026.">

<!-- Good: empty alt on a decorative divider -->
<img src="divider-flourish.svg" alt="" role="presentation">

A useful test: if you removed the image and replaced it with the alt text alone, would a reader still understand the page? If yes, the alt text is doing its job. If not, it is either missing informational content or incorrectly marked as decorative.