Visual media and images can be important elements of digital content. Making them accessible means including “textual equivalents” for all visual elements. A textual equivalent is text that can effectively replace the image in cases where the user cannot access the original, and should serve to communicate whatever the image communicates in this particular context.
Textual equivalents can be adjacent to visual media or can be embedded in the code (usually as “alt text” that is accessed via assistive technology or displayed when the image fails to load).
Alt text refers to an element of code that is connected to an image file. Insert alt text by finding the “alt text” or “description” field in the image upload options.
Keep in mind that alt text should:
Sometimes it is more appropriate to put the textual equivalent directly in the web content, where it is available to all users. This might be the case where the description will benefit many users (e.g. analysis of an artwork) or where the textual equivalent is especially long or complex (e.g. a transcription of an image of a poster or document).
Read more about alt text at Web Aim.
Visual media can be important elements of digital content. Making them accessible means including “textual equivalents” for all visual elements. A textual equivalent is text that can effectively replace the media in cases where the user cannot access the original, and should serve to communicate whatever the media communicates in this particular context.
Three main ways media can be shared in a textual equivalent include captions, subtitles, and transcripts.
Every video should include captions, which include appropriate grammar. Automatic captioning is a good start, but you should always edit captions for accuracy. The captioning key provides an extensive list of best practices for captioning for educational purposes.
Descriptive transcripts are typically text or html files that include spoken and unspoken information in a video. Descriptive transcripts help people with low vision or blindness, but also people who don't have the bandwidth to stream video, and those who prefer written content. The easiest way to start writing a descriptive transcript is use your caption file (without time stamps) and go from there. The captioning key provides an extensive list of best practices for describing media files.
When embedding video into web content check to make sure there is a title in the embed code. This will increase accessibility for people using screen readers and other assistive technologies.
Inside of the embed code html look for "title=", if you don't see a title (usually at the beginning) add it to the beginning of the embed code right after <iframe.
<iframe "title=embedded video"
Information on captions/subtitles from the Web Accessibility Initiative
Basic and descriptive transcripts best practices and how-to from the Web Accessibility Initiative