Making Images Accessible with Alt Text

What Is Alt Text?

Alt text, short for alternative text, is a brief description of an image meant to communicate its purpose to anyone who can’t see it. When a blind person reading a document or web page encounters an image, their screen reader will read the alt text aloud to them.

Everyone Can Benefit from Alt Text

Alt text doesn’t just help users with blindness; it displays wherever pictures fail to load for any of the following reasons:

• Poor internet connection
• The user’s email client has blocked images
• The link to the original image source has broken

Alt text provides a clearer experience for anyone who can’t see your images, no matter the reason.

How Do I Add Alt Text?

Microsoft makes it easy to add alt text to images in most applications. After you insert the image, click “Picture Format” in the toolbar, then select the Alt Text icon. A text box will appear where you can enter a description.

Alternatively, if the image conveys no essential meaning, you can mark it as decorative and screen readers will ignore it.

How Do I Write Quality Alt Text?

• Keep it brief! Aim for 140 characters or less.
• Think about why you’re using the image in the first place. What does it communicate to sighted users? Maybe it’s a place, an action, or an emotional tone. Focus on what matters in context.
• If the image functions as a link or button, describe what will happen when the user clicks.

If an image includes essential text, the alt text must provide the same information. Here, we're adding alt text to a linked image on the PDM web site.

Related

Get more accessibility best practices for text in images.

Resources

• Penn ISC’s guide to alt text
• Brief overview of alt text for complex images (e.g. charts and infographics)
• Microsoft’s guide to writing effective alt text