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Designing alt text

All non-text content must have a text alternative. This alternative should properly describe the element so as not to exclude people who cannot access the visual. 

Alt text for images #

Alternative text for images should

  • be short and descriptive
  • convey the same message to the user that the image would
  • not start with the phrase ‘an image of’, or ‘a photo of’ - this is already provided by the screen reader
  • include punctuation, especially a full-stop at the end – this helps the screen reader take appropriate pauses
  • be filled with a blank (“”) if the image is purely decorative and doesn’t provide any information - this decision tree can help you decide if alt text is necessary

Alt text for data visualisation #

It can be difficult to explain the meaning of graphs, charts and other data visualisation using short alt text. 

Try using Amy Cesal’s model for adding alt text to data visualisation:

Alt = [chart type of type of data where reason for including data]

For example: alt= Pie chart of school admission data from the Department of Education for the year 2022 where 43% of children did not get their preferred choice]

Your alternative text should include a link to the data source.

Complex data visualisations should include a simple explanation of the data for all users in addition to alt text.

Text alternatives for video content #

Video content should include

You don’t have to provide subtitles, transcripts or audio descriptions if you are providing the video as a text alternative. 

Text alternatives for audio content #

Provide a descriptive transcript for audio-only content like podcasts.

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