Images need to provide “alternative text” for accessibility. Alternative text is a textual substitute for non-text content. 

Image Alternative Text Serves Several Functions:

  • Screen readers announce alternative text in place of images, helping users with visual or certain cognitive disabilities perceive the content and function of the images.
  • If an image fails to load or the user has blocked images, the browser will present the alternative text visually in place of the image.
  • Search engines use alternative text and factor it into their assessment of the page purpose and content.

Images Can Enhance Comprehension

It’s easy to assume that images are bad for accessibility, since alt text essentially replaces images with text for users that cannot perceive images. The logical extension of that thought is that text-only sites are ideal for accessibility. However, that logic is flawed—many people can greatly benefit from images while screen reader users are presented with a “text-only” version through appropriate alternative text.

  • Alt text should be a maximum of 250 characters or roughly 40 words.
  • If the image has information that is not written out in surrounding text, you must include it in alt text.
  • If the information is fully described within the surrounding text, you can refer to the existing text description in alt text.

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