One of the most basic and most important considerations for digital accessibility is to make sure that images and other non-text elements have a text alternative (often called alt text). You may have heard, however, that there are exceptions and that not every image requires alt text. That's true, but don't skip the alt text just yet.
To help decide whether you can safely instruct assistive technology to skip over images, ask these three questions first:
- Is the image "pure decoration"?
- Is the image's content repeated in text?
- Does the information make sense without the image?
1. Is the image "pure decoration?"
The Web Content Accessibility Guidelines (WCAG) state that content is purely decorative if it serves "only an aesthetic purpose, providing no information, and having no functionality."
If an image is pure decoration, it doesn't add information and it doesn't prompt or perform an action. Dividers and background images are common examples. Therefore, purely decorative graphics don't need alt text because they don't add value and could even confuse or clutter the screen reader experience.
Read 8 Common Image Alt Text Mistakes to Stop Making to learn more.
2. Is the image's content repeated in text?
One of the reasons alt text is so important is that screen readers and other assistive technologies get their information from digital text, not from the visual presentation of content. Because software can't look at an image and reliably know what's being shown (artificial intelligence isn't there quite yet!), any meaning associated with a graphic needs to also exist in text form.
Sometimes that is already the case without adding more alt text. For example, if an accessible infographic outlines specific steps to doing something and the content is also repeated in text below it, you probably don't need to duplicate all of the information within the image's alt attribute.
Remember three important points when determining if the existing image and text are enough:
- All of the information and meaning needs to be conveyed. If an image shows text, that text usually needs to be repeated verbatim. If an image's purpose is to show a clear trend or point, make sure that is made clear in text, too.
- Images have other accessibility considerations aside from alt text, like color contrast requirements if they include text or important information. Off-screen text alternatives and even visible text alternatives in many cases aren't adequate replacements for making sure the graphic is otherwise accessible.
- Your best bet might be to skip the image and use actual text for everyone. To learn more, read Why Is It Important for Accessibility to Use Actual Text Instead of Images of Text?
3. Does the information make sense without the image?
If you're pretty sure that the experience is better and possibly more-accessible without adding alt text to an image or set of images, put it to the test with this simple exercise: remove it and determine if everything still makes sense.
Is there any information that you could want or need that you aren't getting without the image there? Is it still just as clear what the point of the page is or what to do next?
If you can truly and reasonably say that all information and meaning is equally conveyed with an image entirely absent, it probably doesn't need alt text.
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