As the content expert, it is up to you to determine what alt text is appropriate for your images. You can help make the determination by considering the context of the image. The first question you should ask when writing alternative text for an image is to decide if the image presents content and if the image has a function. If the image has a function, like acting as a link to a different web page, you’ll want to make sure the alt text is short and sweet.
Alt Text Should Typically
- Be accurate and equivalent in presenting the same content and function of the image.
- Be succinct. This means the correct content (if there is content) and function (if there is a function) of the image should be presented as succinctly as is appropriate. Typically, no more than a few words are necessary, though rarely a short sentence or two may be appropriate.
- Not be redundant or provide the same information as text within the context of the image.
- Not use the phrases “image of…” or “graphic of…” to describe the image. It usually apparent to the user that it is an image. And if the image is conveying content, it is typically not necessary that the user know that it is an image that is conveying the content, as opposed to text. If the fact that an image is a photograph or illustration, etc. is important content, it may be useful to include this in alternative text.
Decorative images do not present important content, are used for layout or non-informative purposes. When analyzing an image, determine whether the image is presenting important content. In many cases you can ask the question “If I could not use this image, what would I put in its place?” to determine appropriate alternative text. If you could get rid of the image with no impact to your work, it may be appropriate to add “decorative image” as the alternative text.