Alternative text, or “alt text” describes the content images, graphs and charts. It should be added to every image that conveys meaning in instructional and communication materials including Moodle sites, word processing documents, and slide presentations.
The Purpose of Alt Text
Alt text can be read by assistive technologies, which helps make sure more of your audience can access your content. Alt text has a secondary purpose, too: it can help you, the author, make sure that the image you’ve selected communicates your intended purpose, which can help improve the overall quality of your content. You do not need to include alt text for images and graphics that are purely decorative. However, you should include an empty alt attribute, which we’ll discuss below.
Examples of Alt Text Descriptions
Alt text should answer this question: What is the content conveyed by the image?
The content of the image is not simply a description of the surface features of the image or graphic. Instead, describe what additional content the graphic contains. What information do you want the reader to gain from looking at the image? What is the main idea being expressed by the graphic? Write in simple, precise language, and keep the explanation brief. Typically no more than a few words are necessary, though rarely a short sentence or two may be appropriate.
Possible Alt Text:
- ALT = "George Washington at Valley Forge" (most succinct)
- ALT = "George Washington and Lafayette on horseback talking to soldiers in snow at Valley Forge" (more detailed)
- ALT = "Valley Forge in winter. The landscape is snow covered and soldiers are sitting by the open road with a camp fire.” (emphasizing climate)
Alt Text in Moodle
This is the dialog box that appears when you add an image in Moodle:
Notice the field labeled, “Describe this image for someone who cannot see it.” Place the alt text in this field. If you check the box below it, labeled “Description not necessary”, Moodle will insert an empty alt attribute. This is only acceptable if the image is purely decorative.
Alt Text in Microsoft Word and PowerPoint
Add your image to the Word or PowerPoint document. Now, choose Format > Picture from the dropdown menu (or right click on the image and select “Format picture” from the menu). Click “Alt text”, one of the options on the side bar. Here is the dialog box you will see:
Depending on what version of the application you have on your computer, this may look slightly different. It is important to fill both the “title” and the “description” fields. The title can help the reader decide whether or not they want to read the full description. The description can be longer. Remember you want to describe the purpose of the image to the goal of what you are trying to communicate. The user can hear the title and determine if they wish to hear the longer description.
Adapted from https://accessibility.umn.edu/core-skills/alt-text
After adding an image to a slide or spreadsheet, navigate to the menu: Format > Alt Text. The dialog box looks like this:
Add the full alt text in the Description field and a shorter title in the Title field. The title can help the reader decide whether they want to read the full description.
Empty Alt Attribute
Web-based content is marked up with HTML code that tells your web browser how to display text and images. The HTML image tag looks like this: <img src=“mammoth.jpg”>
The empty attribute (also called “null”) looks like this: <img src=”mammoth.jpg” alt=“ ”>
This attribute lets the screen reader user know that there is an image but that there is no description for it. The attribute is useful where the image is purely decorative but should not be used when the image conveys meaning.
If you’re working with images in a Moodle course web page, you don’t need to worry about this as long as you remember to click the box next to “Description not necessary” (Moodle adds the attribute for you in the HTML view).