Writing Useful Alt Text for Images: Accessibility and Search

Alt text is an image's textual alternative

Alternative text is read by assistive technology when an image conveys information and may be shown when an image cannot load. It should communicate the relevant content or function of that image in its context. It is not a place to repeat every keyword on the page or to describe details that do not help the reader understand the content.

The right description depends on why the image is present. The same photograph may need different alt text in a product listing, a how-to article, or a decorative banner. Read the surrounding text and ask what information would be lost if the image were unavailable.

Write descriptions that fit the context

• Informative image: describe the main information, such as “A line chart showing monthly orders rising from January through June.”
• Functional image: describe the action or destination when an image is the only content of a link or button, such as “Open the product gallery.”
• Product image: identify visible attributes that distinguish the item, not generic claims such as “best quality product.”
• Decorative image: use empty alt text (alt="") when it adds no information and is not interactive.

Avoid starting every description with “image of” unless that distinction matters. Screen readers already announce image semantics in many contexts. Keep the wording concise, specific, and accurate.

Handle complex images carefully

For a detailed chart, diagram, or infographic, a short alt attribute may not carry all the important information. Provide the main takeaway in the alt text and include a nearby text explanation or data table with the details. Do not rely on an image description to make information available only to sighted visitors.

For an image inside a link, avoid duplicating the same label in both the image alt text and adjacent link text. Review the accessible name of the link as a whole, since repeated wording can become tedious for people navigating with a screen reader.

Review alt text as part of publishing

1. Check whether the image is informative, functional, or decorative.
2. Read the paragraph, link, or control around it to understand its purpose.
3. Write only the information needed to use or understand that context.
4. Verify that the text is accurate and not a keyword list.
5. Use an accessibility check and, where practical, test the page with a screen reader.

Good alt text can help search systems interpret image content, but it does not guarantee image-search traffic or higher rankings. Its first job is to make the page's meaning available when the image itself is not.

If your site has many images, an AI tool may suggest draft descriptions. Review each suggestion for accuracy and context before publishing; generated text can invent details that are not visible. ImageTight's alt text generator can be used as a starting point, not an automatic substitute for editorial review.