Creating Accessible Learning: PowerPoint Images and Alt Text
Why It Matters
Individuals who use assistive technology encounter images in very specific ways. It’s up to us to format images so all users can interact with them and glean the same information. One main way to ensure access to images and figures is through the use of alt text.
In PowerPoint, there are certain types of content that assistive technology (AT) reads as “images” beyond typical image files. This can happen within the PPT file itself, or when the PPT file is converted to a PDF.
What counts as an image?
- Images, either copy/pasted or inserted as a file (e.g., .png, .jpg, .tiff)
- Text using “Text Effects”
- Clip art
- Decorative items (e.g., non-text lines)
- Shapes used in both SmartArt and Charts (note: AT will usually read text within these shapes, but shapes are read as images)
Accessibility Guideline: Alt Text
Alt text—short for alternative or alternate text—is a text description of information conveyed by an image. It enables those using assistive technology to glean the same amount and type of info as someone who is looking at the image. Alt text should be brief and should inform the user of the content and function of the image (WCAG 1.1.1, A; WCAG 1.4.5, AA; WCAG 1.4.9, AAA).
Alt text is added to images by the content designer and, in its final form, is typically invisible to those not using assistive tech.
Complex Images & Alt Text
Sometimes images are complex and contain more info than can be summarized in a brief alt text, such as a complicated figure, graph, or complex table. In this case, a two-part alt text is needed: a longer description of the image and a brief alt text attached to the figure itself.
Images that are purely aesthetic and don’t convey any important information to the audience are considered “decorative.” Decorative images don’t require descriptive alt text, but they do require you to take additional steps to ensure AT users interact with the image appropriately.
Add alt text whenever you use images that convey information. If the image doesn't convey info, it's considered decorative.
- Add the image to your slide.
- Note: See page Adding Slide Content, section Adding Graphics, Media, and Tables for how to add images.
- Right click on the image and select “Format Picture” (see Figure 1).
- Alternatively, you can left click the image, select the "Format" tab from the menu ribbon, and select the expand arrow in the "Size" section of the tab.
- The “Format Picture” pane opens on the right side of the screen. Select the “Size & Properties” tab (see Figure 2).
- Click the arrow next to “Alt Text” to open the alt text window. Add your alt text to the “Description” box. Don’t add anything to the “Title” box (see Figure 3).
Use complex alt text when the image is complex (e.g., chart, graph, complex table, etc.) and contains more info than can be summarized in a brief alt text box.
Be sure to include 2 main pieces of content with complex alt text: a longer description of the image and a brief alt text attached to the image itself to tell you where the long description can be found.
- Long description. Write a longer description of the image and include it somewhere within the presentation. Longer descriptions can be formatted as sentences, paragraphs, or even bulleted or numbered lists. Location of longer description could include (but is not limited to):
- Slide text
- Slide Notes section
- Image caption
- Appendix/Notes section
- Link to a page that contains the longer description
- A recorded sound bite of the description
Regular alt text. Add alt text to the image itself to tell the reader what the image is and, if applicable, where the long description of it can be found.
Note: If users have enough context to easily decipher what the image is and what info it conveys, you may not need this alt text.
Example: You use an image of a complex chart, but you also include a text-based title to label the image and an adjacent, detailed caption that explains the chart. Since the user will be able to glean both what the image is and what info it conveys using the title and the caption, you do not need to add brief alt text to the image itself.
A slide entitled, "Steps to Consider in Designing Open Pedagogy Projects" uses an image of a complex decision-tree flow chart to showcase these steps. As seen in Figure 4, the following alt text is added to the image:
A flowchart, formatted as a decision-tree, outlines project design considerations. A text version is found on Slide 11, Appendix 1.
Slide 11, Appendix 1 contains the "long description," or the text-based version of this flow chart (see Figure 5).
A slide entitled, "Figure 9. MVIC % Change & Rest" uses an image with 4 scatter plot charts. As seen in Figure 6, the following alt text is added to the image:
4 scatter plot charts labeled A, B, C, and D. A and B show the relationship between % change in MVIC and pTTD, and C and D show the relationship between % change in MVIC and -dT/dtD. An explanation of these results is found in bulleted text on slide 10.
Slide 10 is a content slide and contains the "long description," or bullet points that summarize the meaning of the 4 scatter plot charts (see Figure 7).
If an image is purely decorative and doesn’t convey any important information to the audience, you can either add the image to a Master Slide or add “decorative” alt text.*
Note: With PPT 2016 and earlier, adding the image to the Master Slide is the only way to truly “hide” the decorative image from AT.
Decorative Alt Text
For PowerPoint 2016 or Earlier
- Open the image’s alt text box (see the How-To: Alt Text tab for how to do this)
- In the “Description” box, add the word decorative.
- If you have multiple decorative images on one slide, group them together and then add decorative to the group’s alt text description. This ensures that only one “decorative” is encountered by the user. (To group, hold down Ctrl + left click all the decorative images. Right click on the bunch and select “Group”).
PowerPoint 2019 or PowerPoint 365
- Right-click on the image and select “Edit Alt Text.”
- Check the box for “Mark as Decorative.”
Add Image to Master Slide
Adding an image to the Master Slide makes the image one with the background. Doing so automatically makes it “decorative” and ensures that assistive tech will ignore it.
To add the image(s) to a Master Slide, you can open the Master Slides (View tab, "Slide Master") and add the image(s) to either a new layout, an existing layout, or a duplicate of an existing layout.
If you’d like to envision the placement of the decorative image(s) with the content, it may be easier to do the following:
- Create a new slide (a regular slide, not a Master Slide) using the appropriate slide layout.
- Add all of your content to slide, ensuring the decorative images are where you want them to be.
- Select all decorative images by holding down Ctrl + left clicking each image. Once they’re all selected, press Ctrl + C to copy them to the clipboard.
- Open the Master Slides by going to the View tab and selecting “Slide Master.”
- Find the template that matches the slide you’re currently using, right click on it, and select “Duplicate.”
- On the duplicate template slide, press Ctrl + V to paste the decorative images exactly where you had them before. In the Slide Master tab, click “Close Master View” to return to your slides.
- Go back to your original slide. While on this slide, go to the Home tab, select the “Layout” drop down, and select the slide template you just created. This will reformat the slide to include the images in the background.
- Delete the decorative images from your slide as you no longer need them.
Rules of Thumb
- Text-based titles. Whenever possible (and especially with complex images), add a text-based label or title to the image so all users know what the image is. "Text-based" means the title is written on the slide, is not contained within the image itself, and likely placed adjacent to the image.
- Verbal descriptions. When presenting a PPT before an audience, always provide a verbal description of images and the info they convey so users of all abilities know what is on the screen.
- Images of text. Avoid using images of text whenever possible, unless it's for decorative purposes or used within a logo.
- Functional images. If an image functions as a link or button, the alt text should describe what the link or button does rather than what the image is. For example, a print icon that, when clicked, prints the page and contains the alt text “print page."