Quick Guide: Writing Alt Text

Screen readers do a lot to ensure a book is accessible by reading the content to the student. This is simple with the text on a page. However, it’s a bit more complicated for images. This guide will explain how alternative text (alt text) is used by screen readers and how to effectively write it for your book.

What Is Alt Text?

Alt text, or alt tag, is a term used to describe text that is read by a screen reader in place of an image. When a screen reader encounters an image, for example, it will skip over it unless there is alt text provided to read in its place.

Alt text usually identifies the type of image (photo vs. graph, for instance) and spells out any relevant details needed for someone who is visually impaired to understand the material. There are two types of alt text to provide: short and long.

  • Short alt text is roughly a single sentence and provides a broad description of the image. In some cases, this may be the only alt text needed. For example, a simple photograph may require a single sentence of explanation.
  • Long alt text can be multiple sentences or paragraphs, depending on the complexity of the image and the type of information that needs to be provided. For example, a graph would always include long alt text, as students will need to hear details about trends and/or specific data points.

How and When Should I Provide Alt Text?

It is important to keep your alt text organized so the production team knows which description goes with which image. The best way to do this is through a simple spreadsheet, which can be provided by your project editor.

Alt text should be provided for every image that is important to a student’s comprehension of the material. This means that, while you will likely skip writing alt text for something decorative such as an icon or a stock photo used as filler, you will be providing for figures such as graphs, charts, maps, and photographs.

Editor’s Tip

Tables are not considered figures and most do not need alt text. Tables should be created using the table tool in Microsoft Word, which will allow a screen reader to read them to students. Only in select cases with highly complex tables will alt text be needed. If you have many complex tables in your book, ask your project editor to go over this with you in more detail.