Alt Text
Alt text is the HTML text description of an image that helps screen readers, appears when an image fails to load, and gives search engines more context about the image.
- Also called
- alternative text
- Applies to
- images
- Commonly confused with
- alt tag
Key points
- Alt text describes images for accessibility and provides context for search engines.
- Best practice is to be descriptive, specific, and concise.
- Avoid keyword stuffing and vague phrases like 'image of'.
- The correct HTML attribute is 'alt', not 'alt tag'.
- CMS platforms usually have a dedicated field for alt text.
How it works
Alt text is added to the <img> tag via the alt attribute. When a browser renders the page, the alt text is available to screen readers. If the image fails to load, the alt text is displayed in its place. Search engines index the alt text as part of the image context, aiding in image search results.
For example, alt text examples like 'black cat sitting on a red sofa' provide more information than 'cat'. This attribute is not the same as the title attribute or caption. Some tools use an ai description generator to create alt text, but manual review is recommended.
The term 'alt tags seo' is often used incorrectly; the proper attribute is 'alt'. In CMS platforms, alt text is usually entered in the image settings or media library rather than coded manually.
Why it matters
Without alt text, users relying on screen readers miss the image's content. Informative images require descriptions to convey meaning. For SEO, alt text helps search engines understand the image, which can improve visibility in image search.
However, its primary purpose is accessibility; keyword stuffing can harm user experience and may be penalised. When used correctly, it supports both accessibility and image seo.
Where it changes your decision
- When an image contains text or data that is not repeated in surrounding copy, alt text must convey that information.
- For decorative images, empty alt text (alt="") is appropriate to avoid clutter.
- In e-commerce product pages, descriptive alt text can help products appear in image search results.
Common mistakes
- Stuffing keywords instead of describing the image naturally – leads to poor user experience and potential penalties.
- Using vague phrases like 'image' or 'photo' – provides no useful description.
- Leaving alt text blank for informative images – fails accessibility.
- Writing alt text that repeats the caption without adding value – redundant.
Questions people ask
What is alt text for images?
Alt text for images is a short description added to the HTML img tag that describes the image content. It is used by screen readers to convey the image to visually impaired users and appears in place of the image if it fails to load. Search engines also use alt text as context for indexing and ranking.
How to write alt text?
Write alt text by describing the image's content or function in a concise, specific way. Start with the most important details, avoid phrases like 'image of' or 'picture of', and use keywords naturally only if they fit the description. For decorative images, use empty alt text (alt=""). Review the image to ensure the description is accurate and useful.
What is alt text on Instagram?
Alt text on Instagram is a field that allows users to add a written description of an image for accessibility. It functions similarly to web alt text but is specific to the platform. When posting or editing a photo, you can enter alt text in the accessibility settings; it is read by screen readers but not displayed publicly.
How to add alt text in word?
In Microsoft Word, right-click the image, select 'Edit Alt Text' from the context menu, and type a description in the panel that opens. This adds an alt attribute to the image in the document, which is preserved when the document is exported to HTML or PDF.
Sources
- Google Search Central Most authoritative source for how Google handles image and on-page SEO signals.
- WebAIM Widely cited accessibility authority for writing effective alt text.
- W3C WAI Standards-based guidance on accessible images and alternative text.
- Yoast Well-known SEO reference that explains image optimization and practical CMS usage.
- Ahrefs Clear SEO-focused guidance on best practices and common alt text mistakes.
Written and maintained by Nora Lindholm. Last updated 27 July 2026.
Spotted an error? Email me — corrections are logged and credited on the entry. Outbound links are unpaid; most are nofollow.