Alt Tags SEO
Alt tags (the alt attribute or alt text) are HTML image descriptions that help search engines and screen readers understand what an image shows.
Key takeaways
- Alt text helps search engines and screen readers understand images.
- Write concise, specific descriptions that include keywords naturally.
- Use null alt (alt="") for decorative images.
- Avoid keyword stuffing, vague text, and duplicate alt text.
- Alt text is a core on-page SEO and accessibility best practice.
Alt text is a small HTML attribute with a big impact on both SEO and accessibility.
Example of Good Alt Text
- Image: A photo of a golden retriever puppy sitting on a green lawn holding a red ball in its mouth.
- Good alt text: "Golden retriever puppy holding a red ball on grass"
- Bad alt text: "puppy" (too vague) or "golden retriever puppy dog pet cute" (keyword stuffing)
- Why it works: It describes the image accurately and concisely, using a relevant keyword ("golden retriever puppy") naturally.
When Should You Use Alt Text?
- Every meaningful image on your website needs alt text.
- Product images in e-commerce: describe the product, color, and key features.
- Infographics and charts: summarize the main data or insight.
- Logos: include the business name (e.g., "SeoWiki logo").
- Decorative images (e.g., background patterns, spacers): use `alt=""` (null alt) so screen readers skip them.
What Alt Text Is Not
- Not a ranking factor on its own – it contributes to image understanding but is not a direct ranking signal.
- Not a replacement for the title attribute – the title attribute shows as a tooltip on hover and is not used by screen readers.
- Not a caption – captions appear below images and are visible to all users; alt text is hidden unless the image fails to load.
- Not a place to stuff keywords – keyword stuffing harms user experience and can be seen as spam.
Quick Start: How to Write Alt Text
- Describe the image accurately – what is the most important visual element?
- Keep it concise – aim for 5-15 words, but be specific.
- Include a relevant keyword naturally – only if it fits the description.
- Use unique alt text for each image – avoid copying the same text.
- End with a period – screen readers pause, improving readability.
- For decorative images, use `alt=""` – never leave the attribute out.
Common Alt Text Mistakes to Avoid
- Leaving alt text blank on meaningful images (e.g., product photos, charts).
- Keyword stuffing – e.g., "buy cheap running shoes online free shipping" for a shoe image.
- Vague descriptions – e.g., "image" or "photo" instead of a real description.
- Repeating the same alt text across multiple different images.
- Forgetting to add alt text to new images added to your site.
Next step
FAQ
Should I use keywords in alt text?
Yes, but only when the keyword naturally fits the image description. Avoid keyword stuffing; focus on describing the image accurately for users.
What is the difference between alt text and title attribute?
Alt text describes the image for search engines and screen readers. The title attribute provides additional tooltip information on hover and is not a replacement for alt text.
Related topics
Sources
- Google Search Central: Images — Best source for how Google understands images and image SEO guidance.
- W3C Web Accessibility Initiative — Authoritative accessibility guidance on alternative text for images.
- Google Search Central: Create helpful, reliable, people-first content — Useful for clarifying that alt text should serve users, not be keyword-stuffed.
Reviewed by Lucía Marín, Founding editor.