What is alternative text?
It is a short text alternative that explains the content and / or function of non-text content (photos, buttons, graphs) in most digital documents such as Adobe Acrobat, Apple Pages and iBooks Author, Google Docs, Microsoft Office and OneNote and of course web pages such as this.
Alternative text can be presented in two ways:
- Within the alternative text field related to the image.
(Sometimes this field might be called alt text or accessibility description)
- Within the text information surrounding the image itself.
What function does alternative text serve?
- It is read by screen readers (such as Apple’s VoiceOver) in place of images. This allows the content and function of the image to be accessible to anyone with a print disability.
- It is displayed in place of the image in web browsers if the image file is not loaded or when the user has chosen not to view images.
- It provides a semantic meaning and description to images which can be read by search engines.
Things to consider before writing alternative text.
What you write as the alternative text really depends upon the context. You need to think about the audience, the purpose of the image and the message you want to convey. Describe the most important aspect(s) of the image first and omit decorative details unless they are crucial to understanding the image. If the image is of text, the description must convey that text to the user. Finally, don’t worry including descriptions to background or purely decorative images.
How do I write great alternative text?
- Think about the context
- Keep it simple
- Keep it short, like a Tweet
Alt text examples
In the examples below I have included the alt text into the caption as well.