When to use images and how to describe them on GOV.WALES.
When to use images
Only use images if they:
- are necessary to explain something which cannot be explained using text, for example a map
- help users understand information in a different way, for example a graph
Text is usually preferred as it:
- is more accessible, for example easier to read using screen magnifiers
- resizes better across devices
- tends to be more visible to search
Avoid images which contain text. Write it in the body text instead.
Describing images (alt text)
Alt text is used as an alternative to an image for people who use assistive technology, like screen reading software.
Alt text must tell people what information the image provides.
Do not add alt text for decorative images, these include images:
- for visual decoration, for example a person, landscape or building
- whose contents have already been described in the surrounding text
When alt text is not added the alt attribute must be empty quote marks (alt=””). To meet this requirement content editors must leave the alt text field blank.
Alt text should be no longer than around 125 characters.
Do not start alt text with ‘image of’ or similar, a screen reader will tell the user an image is present and they do not need to be told twice.
Alt text for charts should include:
- the chart type used (for example, bar chart, line chart)
- the type of data used in the chart (for example, marriage rates, death rates, level of GDP, amount of weekly hours worked)
- a summary of the main point or trend of the chart
For example, when describing the following chart the alt text should be:
Number of treatments undertaken has been fairly stable prior to the pandemic, but has decreased markedly in 2020 to 2021.