Alt Text (Alternative Text)

Alt text (alternative text, alt attribute) is an HTML attribute for images that describes the image content. It has two main functions: Accessibility (screen readers read it for visually impaired users) and SEO (search engines understand the image content). Best practices: be descriptive and precise, naturally include relevant keywords, don't start with "image of" (the browser knows that), use empty alt text (alt="") for decorative images. Length: 125 characters or less. Alt text also appears when the image cannot load. It's more important than the image title tag for SEO.