What is alt text and is there a best practice guide?

Alt text is the short form of alternative text and is used to describe the information of images. This includes images that communicate information, of text or are part of a link or a button. Some examples are an infographic, a screenshot or a submit button.

It appears to users when

  • images are disabled or fail to load
  • screen reader or text-to-speech software is used

If you include images, you must create alt text.

Different image types have different alt text requirements. You can use an alt text decision tree to help you work out what kind of alt text you need.

For more details, read our content design guide to images and alt text.

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Also worth checking out DIAGRAM Center’s free Image Description Guidelines and Accessible Image Sample Book.

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