Section 5 Alternative Text and Long Descriptions
Use Case.
Write useful alternative text/descriptions for images.
Time Commitment.
Minimal to significant. This can vary depending on how many images you need to create alternative text for.
Subsection 5.1 Writing Alt Text and Descriptions
Alt text should convey the purpose of an image. It’s possible that two different instructors use the same image to convey different information. In this case, their alternative texts for the image would not be exactly the same. Alt text should be concise (around 120 characters or less). If an image is complex and cannot be adequately described with alt text, you can include a long description directly in the text next to the image, or link to a separate document. Long descriptions can include more formatting when necessary, like headings, lists, and tables. If an image is adequately described in the text, the alt text can just point users to the surrounding text for the description. If an image is present solely for decorative purposes, it can be marked as such.
AI can be a helpful aid in generating image descriptions. As a starting point, you may try submitting your image with a prompt like “generate an alternative text for this image”. Since only you know your intent for the image, you will likely want to modify the output.
You can also read this advice for writing image descriptions if you’d like more detailed information.
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pretextbook.org/doc/guide/html/topic-accessibility.html#subsec-img-desc-adviceSubsection 5.2 Adding Alt Text and Descriptions to Images
How alternative text is added to an image will vary depending what you are using to create your document. We’ve included some common cases below.
Subsubsection 5.2.1 PreTeXt
Alt text can be added with the .
<shortdescription> tag, while long descriptions can be added with the <description> tag. An image can be marked decorative by setting decorative="yes" as an attribute of the image. This is outlined in the images overview of the PreTeXt guide2
pretextbook.org/doc/guide/html/overview-images.html#overview-images-9Subsubsection 5.2.2 LaTeX
Use the syntax
\includegraphics[alt={Short alt text goes here}]{image.png} to add alt text to your images in LaTeX. See Subsection 2.1 for important details on how to enable tagging and alt text in your LaTeX documents.
To add a long description, include it in a paragraph close to your image, or link to a separate file or appendix.
To mark an image as decorative, use the syntax
\includegraphics[artifact]{image.png}.
Subsubsection 5.2.3 PDF
To add alt text, open your .pdf file in Adobe Acrobat, and select
Tools > Prepare for accessibility > Add alternate text. If the image is decorative, check the "Decorative figure" checkbox and leave the alt text field blank. Note that your document must be properly tagged in order for Adobe to find the images needing alt text.
To add a long description, include it in a paragraph close to your image, or link to a separate file or appendix.
Subsubsection 5.2.4 Word/Powerpoint
To add alt text to an image in Word or Powerpoint, right click the image and select "View Alt Text...". Enter your alt text in the window provided. If the image is decorative, leave the alt text field blank and toggle "Mark as decorative" to on.
To add a long description, include it in a paragraph close to your image, or link to a separate file.
Subsubsection 5.2.5 Canvas
To add alt text to an image in Canvas pages, select the image and then "Image Options". Enter your alt text in the window provided. If the image is decorative, leave the alt text field blank and check the "Decorative Image" checkbox.
To add a long description, include it in a paragraph close to your image, or link to a separate file.
