Alt Attribute SEO
The alt attribute is HTML text added to an image that describes its content or function for search engines and screen readers when the image is unavailable. It is part of the <img> tag.
- Also called
- alt text, alt description, alt tag (shorthand)
- Applies to
- All <img> elements on a web page
- Commonly confused with
- Image captions, image titles, or surrounding text
Key points
- Alt text helps search engines interpret image content because their image recognition is still limited.
- Good alt text is concise and descriptive, describing the image's content or function rather than stuffing keywords.
- For purely decorative images, best practice is to use empty alt text (alt="") so screen readers skip it.
- Keyword stuffing alt text instead of describing the image naturally is a known mistake that can harm relevance.
- Alt text is part of on-page SEO and accessibility, so it should be written for both humans and machines.
Why it matters
Without alt text, search engines have limited ability to understand what an image shows, which reduces image search visibility and the page's topical relevance. For users relying on screen readers, missing or poor alt text blocks access to the image's information or function. The alt attribute is a standard HTML element that directly affects both accessibility compliance and image SEO.
Where it changes your decision
- When adding images to a page: decide whether the image is informative or purely decorative. Informative images need descriptive alt text; decorative images should use empty alt text (alt="") so screen readers skip them.
- When optimising for image search: write concise, natural descriptions that include relevant keywords only if they fit the image's content. Avoid keyword stuffing, which can harm relevance and user experience.
- When auditing existing pages: check for missing alt text, vague descriptions like 'image' or 'photo', and keyword-stuffed alt text. Fix each according to the image's purpose.
Questions people ask
What is image alt text?
Image alt text is the text value of the alt attribute on an <img> tag. It provides a textual alternative for the image when the image cannot be displayed, and it is used by screen readers to describe the image to users who cannot see it. Search engines also use alt text to better understand image content.
How to write alt text?
Write alt text that concisely describes what the image shows or does, using natural language. Include relevant keywords only if they fit the description naturally, and avoid keyword stuffing. For purely decorative images, use empty alt text (alt="") so screen readers skip them.
Does alt text help SEO?
Alt text helps SEO by enabling search engines to interpret image content, which can support image search visibility and the page's topical relevance. However, it is not a direct ranking guarantee; Google uses many signals for image understanding. Modern guidance favours descriptive, user-first text over keyword repetition.
Sources
- Google Search Central Best source for Google’s guidance on image SEO and how Google interprets image text.
- W3C WAI Authoritative accessibility guidance on alternative text and non-text content.
- MDN Web Docs Clear technical reference for the HTML `alt` attribute and proper usage.
Written and maintained by Nora Lindholm. Last updated 27 July 2026.
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