The text equivalent fulfills the same function as the author intended for the non-text content (that is, it conveys all of the intended information and achieves the same function as the non-text content).
Guideline 1.1 (text-equiv) Issues
People who are blind, have low vision, have cognitive disabilities or have trouble reading text for any reason can have the text read aloud to them by assistive technology.
People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation or have it translated and presented as sign language by assistive technology.
People who are deaf-blind can read the text in braille.
Example 1: an image used as a button. (short equivalent for function)
A right arrow icon is used to link to the next slide in a slide show. The text equivalent is "Next Slide," so that a screen reader would read the phrase "Next Slide" and automatically identify it as a link by adding the word link or changing the synthesizer's voice.
Example 2: a data chart. (short label + longer description)
A bar chart compares how many widgets were sold in June, July, and August. The short label says, "Figure one - Sales in June, July and August." The longer description identifies the type of chart or graph, provides a high-level summary of the data comparable to that available from the chart or graph, and provides the data in a table or other accessible format.
Example 3: an animation. (short label + longer description)
An animation shows how to tie a knot. The short label says, "An animation showing how to tie a square knot." The longer explanation describes the hand movements needed to tie the knot.
Example 4: an audio file of a speech. (short label + transcript)
An audio file is embedded in a Web page. The short label says, "Chairman's speech to the assembly." A link to a text transcript is provided immediately after the audio clip.
Example 5: an audio file of a symphony. (short label)
An audio file is embedded in a Web page. The short label says, "Beethoven's 5th Symphony performed by the Vienna Philharmonic Orchestra."