Definition

Alt text is the value of the HTML `alt` attribute on an `<img>` element — a textual description of an image that screen readers announce to users with vision impairments and that search engines use to understand what the image depicts.

Google uses alt text along with surrounding page content as a signal for indexing images and for matching them to image-search queries. Alt text should describe the image accurately and concisely; keyword-stuffed alt text is treated as spam. Decorative images that carry no meaning should use an empty `alt=""` so screen readers skip them, rather than being omitted entirely.

Examples

• Descriptive alt text

  A photo of a brown labrador retrieving a stick is marked up as `<img src="dog.jpg" alt="Brown labrador retrieving a stick on a beach" />`. Screen readers announce that description, and Google has a chance of ranking the image for related queries.

• Decorative image

  A page uses a thin gradient line as a visual divider. It is marked up as `<img src="divider.png" alt="" />` so assistive technology skips it instead of announcing 'image' with no useful description.

Sources

• Google Search Central — Google Images SEO best practices

Related terms

• Meta Description
  A short HTML attribute summarising a page, often used by search engines as the snippet shown beneath a result's title.
• Schema Markup
  Structured data added to a page that describes its content to search engines in a machine-readable format.

Where QueryCatch uses this

• Image Optimisation
• SEO Audit