Alt text (alternative text)
Alt text is a written description of an image that screen readers announce to people who cannot see the image, and that search engines use to understand image content.
Detailed explanation
Alt text — short for "alternative text" — is the value of the HTML `alt` attribute on `<img>` tags. It is read aloud by screen readers, displayed when an image fails to load, and used by Google Image Search and AI crawlers to understand what an image depicts.
WCAG 2.1 Success Criterion 1.1.1 (Non-text Content) requires every meaningful image to have alt text. Decorative images (purely visual flourishes that add no information) should use an empty alt attribute, written `alt=""`, so screen readers skip them rather than announcing the filename.
Good alt text describes the image's purpose, not just its appearance. For a product photo, that means including the product name and any visually distinguishing detail a sighted user can see — color, pattern, key feature.
How this applies to Shopify stores
On Shopify, alt text is set per image in the product editor under Products → [product] → image → Edit alt text. Theme-level alt text comes from Liquid expressions like `{{ image.alt | escape }}`. AccessComply's AltTextAgent generates and applies missing alt text via the Admin API.
Primary source: w3.org