Universal Design for Web Applications

Keys to Writing Good Text Alternatives

Images are used for a variety of purposes, and therefore the requirements for writing the text alternatives depend on the purpose of the image. When penning a text alternative for an image, the first question you should ask yourself is, “What is the purpose of this image?” Is it a graph indicating sales growth of a product? Is it a button that links to the home page? Is it a webcam showing the current weather conditions on campus? Is it a test to determine if the entity interacting with your content is human or a spambot? Is it a piece of art? These are only a few situations in which you might be using a given image. We’ll provide a few examples to help you consider how to write good text alternatives.

Pictures of Recognizable Objects

Any change from nontext content to text involves some amount of signal loss. Your responsibility as an author is to compensate for that lost data as efficiently as possible. It may help to imagine describing the image you’re seeing to someone on the phone. (Try it with lolcats: “It’s this cat looking really surprised and unhappy, and the text says ‘DO NOT WANT!’”)

There is no right answer, strictly speaking, when it comes to alt text. Good alt text is situational and therefore subjective. For example, Figure 3-2 shows a picture.

Figure 3-2. Photo by Rosalie Town in need of a description

How would ...