Image alt text
Also known as alt attribute · alternative text · alt tag
The alt attribute on an <img> provides a text description of the image for screen readers, search engines, and cases where the image fails to load.
What it is
Alt text is the value of an image's alt attribute, describing the image's content or function in words. Screen readers announce it, browsers show it when an image cannot load, and search engines use it to understand and index the image.
Why it matters
Alt text is the primary way crawlers and AI engines understand what an image conveys, enabling image search and richer multimodal answers. It is also a core accessibility requirement, and descriptive alt strengthens topical and entity context that helps your content be cited accurately.
How to verify
Inspect images in DevTools or run document.querySelectorAll('img:not([alt])') in the console to find images missing the attribute. Accessibility audits in Lighthouse, WAVE, or axe report images without alt and flag uninformative alt text.
How to fix
Write concise, specific alt text that conveys each content image's meaning, including relevant keywords only where natural, and keep it under roughly 125 characters. Use empty alt="" for purely decorative images so assistive tech skips them, and never stuff keywords or restate visible captions.
Related terms
- Page performanceHow quickly and smoothly a page loads and becomes interactive, commonly measured by server response time, HTML weight, and Core Web Vitals.
- Single H1 headingThe <h1> is the top-level heading that names the page's main topic; using exactly one gives the document a clear, unambiguous title for users, crawlers, and assistive technology.
- Entity ClarityStating plainly who the brand is, what it does, and its key facts so people and machines can identify the entity without ambiguity.
- Open Graph and Twitter Card tagsOpen Graph and Twitter Card meta tags tell social platforms and chat apps how to render a link preview: its title, description, and image.
Official references
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