What is alt text?

Alternative text (alt text) is text that describes the content of an image that can be read by a screen reader. It's important to consider what elements of the image are important to include in context. A portrait photo of a historical figure may just need that figure's name as the alt text, while a piece of art may need its primary features denoted, and a diagram or graph may need its contents fully described.

What needs alt text?

All images that are used in an instructional or additive manner should be given alt text. Irrelevant images should be marked as decorative (or tagged as background/artifact in .pdf). While "decorative" is the main case in which an image should be ignored, other use cases may also necessitate an image being marked as decorative. An image may convey information, but it may be already stated elsewhere. If the image adds no additional perspective, that image should be marked as decorative. Another example may be an image that's repeated on every page. It may even have an informative role, but in that case the first occurrence should be given alt text, and the repeated instances should be decorative.

General alt text guidelines

  • Alt text should be as concise as possible while still fully describing the important parts of the image. Screen readers read it linearly, so unlike other text, the user cannot jump back to reread portions without reading the entire alt text again.
  • It should not include text like "image of", as that is already provided by the screen reader and would be redundant.
  • It should not include text that is in the caption or repeated elsewhere on the page.
  • It should not provide additional information that is not present in the image itself. For example, if you're alt texting a photo of the moon landing, you may describe the lander, the flag, and Buzz Aldrin, but you shouldn't include the date or that they launched on a Saturn V.
  • Include any text that's present in the image in your alt text, unless it's an unimportant background feature.

Strategies for image alt text in test questions

A faculty member asked about using alt text to describe some images in an online test.  They had an underlying concern that the alt text they provided, in conjunction with the picture might unfairly assist students who did not need the alternative text.  In the context of UIS, we suggested two ways we felt a student could view alt text.  With slow internet speeds in some areas, a slow loading page might load the alt text before the image, or a student could inspect the page to view the alt text.  We came up with two possible solutions to this issue.

  • Simplest option for the student: Create a second copy of the test with alt text added to the pictures, and hide the test.  Provide a similar statement to the syllabus and make that test available for students who need the test.  Currently, our institution uses Blackboard and this option would create some grade book issues when used.
  • A possibility: Add alt text to each image which might have a specific nomenclature such as q1image1, q1image2, q1image3…. Then create a word file that links the q1image1 to the alternative text.  This file could be added to the online class and hidden.  A statement in the syllabus could reflect that students who need alternative text can contact the instructor and the instructor can share that file with the students prior to the test.

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