Writing Alternative Text
Alternative text is a way to describe images in a non-visual manner. It is especially important for users who cannot see the images on a website or for situations where an image is not able to be downloaded by a user’s browser.
Alternative text should describe the image in a brief but complete sentence which includes proper punctuation. It should be included on almost all images. Ultimately, a visitor to your website who views a page without the images loaded should leave the page with as close to as the same knowledge gained as someone who can see the images.
The language used in your alternative text will depend on the purpose of the image. See below for details.
Supporting Imagery #
If the image is a photo that directly supports the other contents on the page, describe the image in detail. People who do not see the image should come away with the same information as if they had.
Charts and Graphs #
If you’re sharing a chart or graph as part of your page, include the data in the alternative text so people have all the important information.
Example: A chart is on the page showing percentage based data of applications to a degree program done on mobile phone. "In 2016, 35% of 5,000 students applied for the School of Public Health's Applied Biostatistics Certificate program by mobile phone."
If the information being conveyed by the chart or graph is too particularly verbose or cannot be explained in a brief sentence, make sure that there is text on the page that accompanies the image. Then, in the alternative text for the chart or graph, provide a brief synopsis of the image and to refer to the text of the page for me detail.
Decorative Imagery #
In general, if an image is added to your page and does not serve a purpose to the content of that page (as described above), then consider not including it.
If you must include an image of this nature, do not specify alternative text. This ends up creating excess language that would be read aloud to those using screen readers and other assistive technology.