Chart titles

Chart titles should be appropriate, detailing the main message, key point or trend the chart is demonstrating.

Chart titles should be:

• front-loaded
• in the active voice
• in sentence case
• as concise as possible
• 15 words or fewer

For example, ‘Croydon has the most monetary transactions out of all suppliers’.

Chart titles should also be tagged correctly. Whether you publish your chart in a document or on a webpage, the background code will have ‘tags’ for the heading structure.

Tags help users understand the structure of the document. They do this by putting visual cues on section headings and subheadings (for example, different font sizes and bold text).
They also help screen reader users to better understand document structure. Screen reader software reads out tags and screen reader users use them to find the content they need.

Chart subtitles

Chart subtitles should provide a specific description of the data used in the chart. This must include the:

• statistical measure
• geographic coverage
• time-period

For example, ‘Sum of all transactions (£) from Jan 2025 to Feb 2025 by supplier.’

For more information refer to the ONS guide on chart titles and subtitles

Chart labels

Any text that has to live within a chart, such as axis labels, data labels, annotations or legends should be made as accessible as possible.

Use a font size large enough for all labels to be legible. As images often get resized when published, it is not possible to suggest a specific minimum font size. Instead, this is something that needs to be judged when creating the chart.

All text should be horizontal. If it is difficult to fit the chart labels into the space, try transposing the chart or changing the units. You could also drop some of the labels.
For example, only label every other year in a time series. If you do this, use tick marks to show the regularity of the data.

Commas should be used to separate thousands on chart label values, for example 9,000.

Only use colours that have the required level of contrast with the background. See the Colours guidance for more information on this.

Chart legends

Avoid legends where possible. If legends are used, the layout should be stated, and any lines and categories should be labelled directly.

Bar charts

If legends are used, they should be presented in the same order and orientation as the stacks in the bars, or the bars in the clusters. The legend layout should be stated just above the chart. Users can then match labels using positioning alongside colour, or alternative encoding methods.

Line charts

Try to place labels at the end of the lines, on the right-hand side of the chart. Legends rely on users matching labels to lines using colours which can be difficult for some users. Therefore, legends should only be used when essential, for example when lines are very close together.

Pie and doughnut charts

Categories should be labelled directly. Legends and keys rely on users matching labels to categories using colour alone. This fails accessibility success criterion 1.4.1 Use of Colour.

For more information about subtitles and legends, visit the Government Analytics Framework accessible charts checklist.

Chart layout

Chart titles, source information and footnotes should be placed in the body text, or as separate text, rather than in an image.

Presenting titles, source information and footnotes within an image may fail accessibility success criterion 1.4.5 Images of Text. Images of text may be difficult for some people to read and users of screen reader software would be likely to miss this content completely.

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