Alt Text and Image Descriptions: What, why, how

This article introduces staff, students, and faculty to the core accessibility concept of alt text (alternative text) and also longer alt text referred to as image description. 

What is Alt Text?  

Alt text, or alternative text, is a brief description of a digital image or graphic that is read aloud by screen readers, technology that reads digital content aloud. A sighted user can see what is on an image, and a person using a screen reader (oftentimes a non-sighted user) then has the same information read aloud about what information is on the image. This is what is meant by equitable access, we all get to know what is on an image! 

Oftentimes alt text refers to shorter descriptions (about 120 characters or less) that you type into the alt text feature, whereas Image Description refers to lengthier descriptions that may be built into the body of a message so sighted users could also read it. And, it's ok to use the words interchangeably. 

Regardless of whether you call it alt text or image description, there is a need to have written text as an alternative way for someone to know about what is on an image. 

Why Alt Text Matters

Anyone who accesses digital content by using screen reader software must have the alt text or image description read aloud. Many people around the world use screen readers!

• Most screen reader users are blind or have low vision. Screen readers are also used by other individuals with cognitive disabilities, learning disabilities, or multiple disabilities.
• In addition, some people simply find it helpful to listen to content read instead of other methods of reading.  
• An added benefit to Alt Text is that if an image fails to load, the alt text will be displayed in the body of that document or message in place of the image.  

Basic How To's

• Start by committing to this concept: any image needs to have a written description as a second method of access. This includes photos, infographics, images in slides or emails, social media, etc. Some people will see the image with their eyes and decipher the meaning that way, and those who use screen readers need the image spoken aloud. 
• Get into the habit of looking for the alt text feature in the tools you use.  
• Most images would require alt text; however, at times an image is marked decorative if you decide it is purely decorative such as stylistic borders. If you mark an image decorative, screen reader users hear that it is a decorative image. 
• Most software, course platforms, and websites have a feature called Alt Text. As you create content that includes an image, type in alt text. For example:  
  • When creating a Word document that includes an image, locate the Alt Text accessibility feature to add in the description before sharing the image. This 2 minute Microsoft video demos how to create accessible word docs by adding in alt text
  • When creating content in Canvas, use the built-in accessibility tools including alt text. 
  • Practice creating accessible emails. Take an email you already want to develop and send after you first locate the Check Accessibility and then click on your image to add alt text. 
  • When using PowerPoint, refer to this guide: Alternative Alt Text in PowerPoints. 
• At times a platform does not have a way to add in alt text, or perhaps you need a longer alt text and there is a character number limit to the built in alt text feature in a given tool. In those cases, a more extensive image description could be created and either typed in before or after the image. 
• When using AI to generate alt text, also have a human review and correct as needed. AI can get you started and save time!  

Additional Resources 

• Enroll in the Digital Accessibility Basics Badge site; learn more about alt text and other digital accessibility skills.  
• Read: Everything you need to know to write effective alt text (Microsoft article)