Accessibility guidelines for alt text

Screen readers read alt text of an image aloud to enable people with visual impairments and other disabilities to understand important images.

It’s best to use simple language to describe what the image shows and the value it adds to the document. Avoid using complicated language, acronyms, slang and jargon.

A screen reader will specify that an image is an image, so there’s no need to write the words ‘image of’ or ‘photo of’ in the alt text.

Instead of: An image of a fox diving headfirst into snow.

Write: A fox diving headfirst into snow.

Include a concise description of what you see in the picture.

Here’s an example of how a caption and alt text can complement one another and provide greater context for screen reader users.

Caption: ‘Surveys have now resumed in the Afar region to check people’s eyes for signs of trachoma.

Alt text: ‘An eye health worker wearing a surgical mask checks a boy’s eyes.’

Provide a text equivalent of the information presented in a graph.

It is helpful to include what type of chart you are describing and any meaningful data.

Instead of: Bar chart of the number of participants who found the design workshop accessible.

Write: The bar chart shows the number of participants who found the design workshop accessible. The majority of participants either agreed or strongly agreed that the workshop was accessible.

Screen readers only read out about 125 characters for alt text, so you will need to write succinctly.

If you require more space for any valuable information, write it in the image caption or consider including it in the main copy.

Images and graphics that aren’t essential for understanding the content, such as background graphics, icons and generic images, should be marked as decorative.

This will tell a screen reader to ignore them when reading page content.

It helps screen reader users avoid unnecessary audio ‘clutter’ when they’re trying to navigate a page, enabling them to focus on the most important content.

You should also mark an image as decorative if it already has a caption that contains the information you want to convey. Alt text that contains the same information as the caption is of no benefit to screen reader users.

To mark an item as decorative, type empty quote marks (“”) into the alt text field. Some software also has a ‘Mark as decorative’ check box in the alt text pane.

1. Right-click on an image with your mouse.
2. Select Edit Alt text.
3. A box will appear on the right-hand side.
4. Type your alt text into the box.
5. Do not rely on Microsoft’s auto-generated alt text as it is not sufficient.
6. You can turn off Microsoft’s auto alt text by going to File and then Accessibility and making sure there is no checkmark in the ‘automatically generated alt text for me’ box.
7. To mark something as decorative, follow the same steps but check the ‘mark as decorative’ box instead of writing alt text.

1. If possible, when converting from Microsoft Office to PDF, use Adobe Acrobat to ensure all accessibility elements are picked up.
2. Check for accessibility issues in Adobe Acrobat by selecting Accessibility in the Tools menu. It will open a toolbar.
3. You can identify tagging, reading order and accessibility problems by selecting Accessibility Check.
4. Write alternative text by selecting Set Alternate Text.