Definition
The alt attribute (alternative text) is an attribute of the HTML img tag that provides a text description of the image. It serves two essential functions: accessibility (screen readers read the alt for visually impaired users) and SEO (Google uses alt to understand image content and index it in Google Images). Good alt text is descriptive, concise (under 125 characters), contains the keyword when relevant, and actually describes the visual content of the image.
Key Points
- Essential for accessibility and image SEO
- Must describe the visual content of the image concisely
- Include keyword when relevant, without stuffing
Practical Examples
Product image
The alt 'Nike Air Zoom Pegasus 41 blue running shoe side view' is descriptive, contains the keyword, and describes the image.
Decorative image
For a purely decorative image (separator, ornament), alt should be empty (alt='') to tell screen readers to ignore it.
Frequently Asked Questions
Technically no in HTML, but it's mandatory for accessibility (WCAG) and strongly recommended for SEO. Google uses it as the primary signal to understand images.
Only when relevant and natural. Describe what the image shows. Keyword stuffing in alts can be considered spam by Google.
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Last updated: 2026-02-07