Quality alt text is essential to provide an accessible experience to users who are blind or have low vision, as it is commonly relied upon by screen readers and other accessibility software. It also acts as a fallback when images and other content are prevented from loading in, which some users may intentionally configure to reduce distractions or conserve bandwidth.

Writing Effective Alt Text

Writing effective alt text requires careful thinking about the context and purpose of images. Because alt text is normally not shown to most learners without the use of assistive technologies, it is crucial that the main text related to the image (not the alt text) establishes the image’s context and purpose. In this way, the alt text then conveys only what’s needed to draw the connection between the image and what’s conveyed about it in the main text. Alt text should therefore be kept as concise as possible.

Using the Canvas Accessibility Checker to Fix Alt Text

The Accessibility Checker will highlight images (1) it detects alt text issues with. The side panel will provide a description of the issue it detected (3) and a field to edit the image's alt text (2). The information icon (4) can be clicked to see more details about the issue.

After making corrections, click the Apply button to save the changes.

Alt Text Length

The Accessibility Checker will flag images with alt text exceeding 120 characters. There is no strict requirement for the length of alt text, but alt text should be kept concise. Longer descriptions should be provided in the main text of the page, rather than in alt text, so that it is useful for all readers.

File Names or Missing Alt Text

When no alt text is provided, Canvas will by default leave the image's file name in its place. The Accessibility Checker will flag this as an issue to correct, since alt text should be provided for any informative non-text content.

Decorative Images

The Canvas Accessibility Checker can’t determine if an image is informative or decorative, but it will give you an option to mark the image as decorative (or provide alternative text description) as you are inserting it.

If you’re looking to enhance the accessibility and inclusivity of your course and teaching, CITL's Universal Design for Learning (UDL) Team can help. For more information, contact the UDL Team at CITL-UDLTeam@illinois.edu.