Alt Text, alternative text for images

Topics

Tip:

The alt attribute (“alt text”) is used to provide an alternative to the image for users who can’t see it.

Best practice

  • Give all HTML <img> elements an alt attribute.
  • Give any decorative images an empty alt attribute ( alt="" ).
  • Describe (for non-visual readers) the contents and purpose of the image in the alternate text.
  • If an alt attribute is not inserted in the Media Library, this will be interpreted as alt="" in the front end.
  • If an image contains a link, the alt attribute should contain the target of that link (e.g. the post title), and not a description of the image.
  • When possible, use CSS to insert images that are only decorative, like an icon or ornament.

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Code examples

<img src="../../gallery/illustration.png" alt="description of the illustration">
Correct: will be interpreted as "description of the illustration, image" (example by Apple VoiceOver)

<img src="../../gallery/illustration.png" alt="">
Correct: will be interpreted as "image" (example by Apple VoiceOver)

<a href="blog.html"><img src="icon.png" alt="Blog Postings"></a>
Correct: will be interpreted as "link, image Blog Postings, image" (example by Apple VoiceOver)

<img src="../../gallery/illustration.png">
<img src="illustration.png">
False: will both be interpreted as "illustration.png, image" (example by Apple VoiceOver)

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Visual example

Screen shot of add image modal in the editor
Image from WordPress Media Library where you can insert various meta-information for an image. An alternative text can be inserted in the Alt Text-field

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Inserting alt attributes

An alt attribute should always be present. The content of the alt attribute depends on the relevance of the image for understanding that context.

An alt attribute with a description should be added:

  • images that contain text that is not provided nearby
  • images that illustrate the content in the broadest sense
  • images with complex information should be described briefly in the alt attribute, and the information should be provided elsewhere on the page

An alt attribute with text describing the target should be added:

  • images that contain a link

An empty alt attribute (alt="") should be added:

  • when images are decorative; but it is better to insert such images using CSS

If an alt attribute is not present, the filename of that image may be used instead. Read more on Are alt attributes required? Always?

On the Web Accessibility Tutorials of the W3C the alt Decision Tree tool is an almost comprehensive guide that describes how to use the alt attribute of an image in various situations.

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Benefits

Blind, people with visual and readability limitations will benefit when using a screen reader.

The alt attribute helps with Search Engine Optimization. Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image (source https://support.google.com/webmasters/answer/114016).

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WCAG 2.1 Success Criterion

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