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Library and Learning Services Accessibility Help Guide: Images and Alt text

An internal guide for Sheridan Library staff to answer their questions about accessibility, UDL and AODA requirements.

Images and Alt Text

Alt text is used to describe images, graphs and other media used in presentations, websites, and other documents. Blind and low vision users require alt text to understand what an image is showing them through their assistive technology software. Alt text should accurately describe the image so the user can understand all the crucial information provided in the image. Screen readers cannot read images, graphs, etc, unless alt text is provided. Without alt text, this creates a barrier to learning.

Alt text is not only beneficial to those with low vision, blind, but also can be helpful for certain cognitive disabilities as well. Alt text can be helpful in other ways too. For example, if an image isn't loading on a website a user can still determine what image is of by the alt text. It also allows search engines to find the images in their searches.

Alt text tips

  • Provide a brief explanation of the image and yet still keep it meaningful to the user. Do not leave out crucial information that would be helpful to the user.
  • No more than a few words are necessary, or even just a few sentences is fine. Try to keep the alt text short, kind of like writing a 'tweet'. 
  • Use regular punctuation marks such as full stops and commas, so it can be read in a more human way by a screen reader.
  •  Avoids redundant phrases such as "image of…” or “photo of..." since screen readers already indicate this information when they are reading the content
  • Think about how you would describe the image and it's context to someone blind or with low vision. According to Microsoft Word, when creating alt text "include the following info: the subject(s) in detail, the setting of the image, the actions or interactions, other relevant info"

Where to add alt text?

  • Microsoft Word: Right click your image in the document and then click edit alternate text. It automatically generates alt text for you which you can edit.
  • PDFs in Acrobat DC: Tools - Accessibility - Set Alternate text
  • Powerpoint slides: Once you have added in your image, right click and then select edit alternate text. Like Word, it generates alt text for you which you can edit. 

Decorative images such as clip art or a graphic which is used for decorative purposes, do not need alt text. They are ignored by assistive technologies and are not relevant for the user. 

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