When making digital technology accessible for people using screen readers, the implementation may be of varying levels of complexity, but the task is, in most situations, relatively straightforward: "Is this element labeled and viewable to the screen reader or not?" When we discuss accessibility, we generally are referring to websites, but this holds true for the vast majority of other modern digital interfaces including apps, desktop software, even operating system UIs. Images tend to be a major part of nearly all modern interfaces and can pose a challenge due to the more nuanced considerations that need to be made when ensuring they are perceivable and informative.

The World Wide Web Consortium's (W3C) Alt Text decision tree provides an extensive roadmap to follow to provide the right sort of Alt Text for many different situations. By answering the questions detailed in the decision tree, you are guided to instructions on what style of Alt Text should be used for your particular situation. In some instances, you will be given a brief set of instructions, but in most cases, you will be directed to another page containing detailed information on best practices for composing Alt Text for your particular image.

To illustrate how this process functions, I will follow the tree for a hypothetical image. For our example, we will be designing alt text for a bronze statue pictured on a page about an archaeological dig. Below, I detail the questions and answers that take us to the information on how to compose Alt Text for this image:

  • Q: Does the image contain text?
  • A: No > Continue
  • Q: Does the image contribute meaning to the current page or context?
  • A: Yes, and it’s a simple graphic or photograph.

After answering this final question, we are led to our answer. In this case, "Use a brief description of the image in a way that conveys that meaning in the alt attribute. See Informative Images." Our image supplements other information on the page, namely details on the statue itself that was discovered. In this case, we can use simple text, such as "An image of a bronze statuette." In the text of the page, we will provide greater detail on the statue.

As mentioned in the Alt Text decision tree, there are other cases where the tree will not have a straightforward answer for your particular situation. In those cases, there are many other resources available online for composing Alt Text. In the recent Winter 2024 issue of AccessWorld, I included an article on Alt Text and Audio Description where I detail some tips and tricks for composing both types of description along with links to various other resources to aid in the creation of this content.

If you are looking for a good source of knowledge on anything related to web accessibility, which also can be applied to other situations in many cases, the W3C is a fantastic resource. We frequently evoke this organization in discussions of accessibility due to their creation of the Web Content Accessibility Guidelines (WCAG), which is the premier resource for information on how to make the web accessible to people with a range of disabilities. The W3C includes a host of other informative resources, including self-paced courses on learning web languages, such as HTML and JavaScript, which are accessible to users of assistive technology.