Alt Attribute SEO
Provides a text alternative for an image so search engines and screen readers can understand its content when the image cannot be displayed.
If you have ever stuffed keywords into every image description hoping for a ranking boost, you already know alt text helps relevance more than it guarantees position.
Key points
- Describe the image's content or function, not the page's keywords.
- Use empty alt text (
alt="") for purely decorative images so screen readers skip them. - Keep alt text concise and specific, typically under 125 characters.
- Treat alt text as an accessibility requirement first, an image seo signal second.
- Avoid vague labels like "image" or "photo" — they add no value for users or search engines.
A product page with two images, one alt text mistake
An online shop sells a red leather backpack. The main image has alt text "red leather backpack with brass zippers" — descriptive. A second image, a lifestyle shot of the backpack on a model, uses alt text "backpack" — vague. A screen reader user hears only "backpack" and misses the context. In image search, the first image ranks for "red leather backpack" while the second is invisible. The fix: write alt text that describes what each image shows, not a generic label.
Three ways alt text goes wrong
- Keyword stuffing Repeating target keywords in every image description instead of describing the image naturally. This harms accessibility and can look spammy to search engines.
- Missing alt text Leaving important images without any alt attribute means screen readers and search engines get no information, hurting both accessibility and image understanding.
- Vague descriptions Using text like "image" or "photo" instead of a meaningful description. This adds no context for users who cannot see the image and wastes an SEO opportunity.
Three things alt text is not
- A ranking guarantee Alt text helps search engines understand image content, but is not a direct ranking signal. It supports relevance, not position.
- A caption Captions appear below images and are visible to all users. Alt text is hidden and used when the image cannot be displayed or is read by assistive technology.
- A substitute for content Alt text cannot replace surrounding text or headings. It is a supplement when the image is unavailable, not a replacement for well-written page content.
Common questions
Does alt text help SEO?
Yes, but indirectly. It helps search engines understand image content, improving image search visibility and page relevance.
How to write alt text for images?
Describe the image's content or function concisely, using natural language. Avoid keywords unless they genuinely describe the image.
What is the difference between alt text and a title attribute?
Alt text is a text alternative for the image when it cannot be displayed. The title attribute provides tooltip information, often optional.
Sources
- Google Search Central Guidance on image SEO and alt text best practices
- W3C WAI Accessibility standards for alt text and decorative images
- MDN Web Docs Technical documentation on the HTML alt attribute