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.

Also called: alt attribute, alt text
Applies to: images on web pages
Commonly confused with: image title attribute, caption

Key points

Alt text helps search engines interpret image content and supports image search visibility.
Good alt text is concise, specific, and descriptive of the image content.
Each important image should have unique alt text that matches that specific image.
Including a relevant keyword is acceptable when it fits naturally, but keyword stuffing is discouraged.
Alt text is a core accessibility feature for users who cannot see images.

Why it matters

Alt text directly affects two areas: accessibility and search visibility. For users relying on screen readers, missing or poor alt text makes image content inaccessible. For search engines, alt text provides the only reliable textual signal about what an image depicts. Without it, Google cannot index the image for relevant queries, and the page loses a chance to appear in image search results. Alt text also supports topical relevance when it describes the image in a way that aligns with the page content. Because alt text is part of on-page SEO, neglecting it weakens the overall optimisation effort.

Google has not confirmed alt text as a direct ranking factor for web search, but it is widely accepted as important for image SEO and contextual signals.

Where it changes your decision

When adding product images to an e-commerce page: write alt text that describes the product and includes a natural keyword, because it helps the image appear in shopping-related image searches.
When publishing charts or infographics: write detailed alt text that conveys the data or key takeaway, because screen-reader users rely on that description to understand the visual information.
When using decorative images: set the alt attribute to an empty string (alt="") so assistive technologies ignore them, because describing decorative images adds noise for users.

What it is not

Belief: Alt text is a ranking hack for web search. Correction: Alt text primarily helps image understanding and accessibility; it is not a standalone ranking factor for Google web results.
Belief: Alt text is the same as the image title attribute. Correction: The title attribute provides tooltip text and is not used by search engines for indexing; alt text is the primary descriptor.
Belief: Alt text should be a long description. Correction: Alt text should be concise; for complex images, a separate long description can be provided, but the alt attribute itself should be brief.
Belief: Alt text is optional for all images. Correction: Informative images require alt text; decorative images should have empty alt text to avoid confusion.

Common mistakes

Mistake: Leaving the alt attribute blank on meaningful images. Consequence: Screen readers announce the image file name or skip it entirely, and search engines lose context.
Mistake: Stuffing alt text with keywords instead of describing the image naturally. Consequence: Google may treat this as spammy and the text becomes unhelpful for users.
Mistake: Using vague text like "image" or "photo" as alt text. Consequence: Provides no useful information to users or search engines.
Mistake: Repeating the same alt text across multiple different images. Consequence: Creates duplicate descriptions that fail to distinguish images, reducing relevance for each.

Questions people ask

What is alt text for images?

Alt text for images is an HTML attribute added to an image tag that provides a text description of the image. It is used by screen readers to convey the image content to users who cannot see it, and by search engines to understand what the image shows. Alt text also appears as fallback text if the image fails to load.

How to write alt text?

Write alt text by describing the image content concisely and specifically. Start with what the image shows, include relevant context from the page, and use a natural keyword only if it fits. Avoid phrases like "image of" or "picture of". For decorative images, use an empty alt attribute (alt="") to hide them from assistive technology.

Alt text best practices?

Best practices for alt text include: keep descriptions concise (usually under 125 characters), make each alt text unique to its image, describe the image's function or content rather than its appearance, and avoid keyword stuffing. For complex images like charts, provide a longer description elsewhere. Always use the alt attribute on every image, even if empty for decorative ones.

What is alt text for?

Alt text serves two main purposes: accessibility and SEO. For accessibility, it provides a text alternative for users who cannot see the image, such as those using screen readers. For SEO, it helps search engines understand the image content, which can improve the image's visibility in image search and support the page's topical relevance.

Sources

Google Search Central 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: Images and image search best practices Explains how image alt text helps Google understand image context.
Google Search Central: Create helpful, reliable, people-first content Useful for clarifying that alt text should serve users, not be keyword-stuffed.

Written and maintained by Nora Lindholm. Last updated 27 July 2026.

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