Alternative Text

Alternative text (alt text) is added to images and charts so that people who cannot see them can still have an understanding of the content. 

Alt text is not always needed. Below is a guide for determining if and what kind of alt text is needed. Use caution with AI-generated alt text – this is one thing that's best handled by humans.

When Should I Use Alt Text?

An image does not need alt text if:

• It’s redundant to text immediately surrounding it (e.g. portrait image next to a person's name)
• It has a descriptive caption
• It has no meaningful purpose (e.g. a line or shape)

Images that don’t need alt text can be marked as decorative or coded as alt="".

If you’re not sure whether an image needs alt text, try using the Web Accessibility Initiative’s alt text decision tree.

How Do I Write Alt Text?

Alt text should be concise and describe what the image is, not just what it looks like. This can depend on the purpose of and audience for an image. 

There is no one-size-fits-all formula for writing alt text. Let's use a map for an example.

• If the map is a background image, the alt text could be "Map of the Midwest region of the United States." Or it may be marked decorative if it truly conveys no meaning.
• If the map is used as a representation of what a map looks like, the alt text could be "A map depicting roads, lakes and rivers with lines and cities with dots."
• If the map is used in content about geography the alt text could be "A map showing the distance from Chicago to DeKalb is 65 miles and major interstates that can be traveled to reach each destination (I-88, I-355, I-290)."

Design best practices suggest that any image used should have purpose and meaning, so it's likely your image will need it. If you are not sure what to write, just describe the image as if you are explaining it to someone who can't see it.

Tools for Alt Text

Microsoft Word and PowerPoint

• Microsoft Word and PowerPoint both can generate alt text using artificial intelligence. Click “Generate alt text for me” in the alt text editor or “Generate description” in the accessibility checker. Be sure to check the alt text carefully and revise if necessary.
• For efficiency, use the accessibility checker in Microsoft Word and PowerPoint to quickly move between any images that are missing alt text instead of going to each image or slide manually.

Blackboard Ally

• Blackboard Ally can generate alt text for images that have been uploaded directly to Blackboard as a file. Remember to verify and revise the alt text before saving.
• Coming soon: Ally will be able to generate and add alt text to images within PDFs.

Adobe Acrobat

• This guidance applies for course materials only. Content posted to an NIU website should not be in PDF format.
• Use the accessibility checker in Adobe Acrobat to quickly identify and add alt text to images.
• Review existing alt text using the tags tree by finding tags and opening the tag Properties.
• If you have a source file for the PDF, add the alt text there instead of in the converted PDF. Even better: post the source file instead of the PDF.

Image Accessibility Creator - Arizona State University

The ASU Image Accessibility Creator uses GPT-4o to generate alt text and detailed descriptions of images. This tool works best when you have an individual image file as opposed to images embedded in other files, as you can only upload JPG, PNG, and JPEG file types.

Unlike using an AI platform directly to generate alternative text, images uploaded to the ASU Image Accessibility Creator are not saved or used to improve the AI training or models.

AltTexty

AltTexty Alternative Text Generator uses Google Gemini AI to produce alt text and detailed descriptions of images. As with the ASU Image Accessibility Creator, this tool works best when you have an individual image file to upload. A robust description of the image is produced.