Alt Text

Alt text, also called "alt tags" and "alt descriptions”, refers to the description of images which are read aloud to users on a screen reader. Alt text is not in the body of the document but is attached to the image or object. Adding alt text allows authors to include images and other objects, but still provide the content in an alternative text based format for visually impaired readers. The Microsoft Accessibility Checker will show an error if an image or object does not contain alt text.


Functions of Alt Text

  • Individuals relying on screen readers will use the alt text so they can interpret visual information as well as text. It allows the content and function of the image to be accessible to those with visual or certain cognitive disabilities.  

  • It is displayed in place of the image in browsers if the image file is not loaded or when the user has chosen not to view images. 

  • It provides a meaning and description to images which can be read by search engines or be used to later determine the content of the image from page context alone. 


When is ALT text needed? 

It is necessary to add Alt Text to all graphics in documents and emails. This includes pictures, shapes, charts, tables and graphics. The alt text may however be “” or an empty alt attribute if the content of the graphic is redundant. 

When is ALT text not needed? 

It is not always necessary to add ALT text to images, such as in the following situations: 

  • If the information provided by the image is communicated effectively elsewhere in the body text of the page. Often images (or diagrams) are used to reinforce understanding and do not necessarily provide any additional information. Providing Alt Text in this situation would duplicate text content. 

  • If an image is purely decorative and provides no useful information to the user to aid them in understanding the content of the web page. 


How to Write Alt Text

Alt Text should: 

  • Be accurate and equivalent in presenting the same content and function as presented by the image. 

  • Be short. Typically no more than a few words are necessary, though sometimes a short sentence or two may be appropriate. The longer your alternative text, the more difficult it will be to read by text browsers. A good rule of thumb for alternative text is to keep it between 5 and 15 words total. 

  • Be context driven. The way you write alt text is very dependent upon the accompanying text in a document. For example, if a paragraph of text about George Washington is accompanied by a picture of George Washington the alt text for the picture can be “ “, which indicates that the picture is redundant. If however, a paragraph of text about Presidents of the United States is accompanied by the same picture of George Washington, the picture’s alt text should now read “George Washington, the first President of the United States” 

  • NOT be redundant or provide the exact same information as text within the context of the image. (see above) 

  • NOT use the phrases "image of ..." or "graphic of ..." to describe the image. It’s usually apparent to the user that it is an image. And if the image is conveying content, it is typically not necessary that the user knows that it is an image that is conveying the content, as opposed to text.  

  • Include any text contained in images: If you have images which contain text, the alt-text should be the text in the image unless all the text appears in the document as well. 


The main question you should ask yourself is, “Why is this image used? What message it supposed to convey?”  

For example, the picture below when used  accompanying an article about the type of people who watch and enjoy basketball could have alt text that reads: “A large, diverse group of spectators, standing up and cheering on the bleachers at a basketball game.” 

The same picture when used to accompany an article about the Cortland basketball team could have the alt text: “The crowd reacting as Cortland wins a basketball game 

When used with an article about places you’d find a lot of people, the alt text could read: “A crowd at a basketball game. 

A large, diverse group of cheering students, standing up and fist-pumping on the bleachers of a basketball game

Remember that the point of alt text is to define the images for your readers.  


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Article ID: 137792
Thu 1/27/22 3:38 PM
Mon 3/14/22 1:07 PM