Source XML in formats such as DocBook, JATS, or DITA are often transformed into HTML for delivery, inclusion in an EPUB, or for formatting. HTML may also be used as the source document. HTML source documents may likewise be transformed into different HTML for delivery. The output HTML may include, for example: a new or updated Table of Contents; changed or additional metadata; or, for use with CSS Paged Media, additional copies of content to be removed from the flow and used in running headers and footers.

The first step in making accessible HTML is to use the most appropriate element whenever possible.

How HTML is presented in the browser, including dynamic content, user interface controls, and accessibility APIs, is out of scope for this paper. Important standards in this area include WAI-ARIA 1.1 [WAIARIA] and the rest of the WAI-ARIA 1.1 suite of specifications [WAIARIASUITE].