Documents are described as accessible when they support assistive technology to enable more people to view, read, or interact with the material. For example, a text-to-speech screen reader program might take a blind person through a table in a document by saying something like, “Start of table. First row. The first entry is a column head: Year.”
Besides that making your output documents accessible is beneficial to your readers, increasingly publishers, employers, and governments are mandating that documents meet the relevant standards.
Most TeX and LaTeX authors target output in PDF. In recent years, TeX developers have spent a great deal of effort to enable PDF's created with TeX to be accessible. Their work has been supported by the TeX Users Group.
Making documents accessible involves adding “tags” inside the PDF, which provide additional description of the material. Examples are marking text as a section title, including an alternate textual description of a diagram, or providing a structured description of a formula (as MathML).
The goal for the continuing work is to make LaTeX, to the extent possible, automatically produce accessible PDF output, without authors doing extra work. The LaTeX Project team continues to make regular progress; see the team report from the 2024 TUG meeting.
Although the interface is still subject to change, right now LaTeX authors can experiment with making accessible files. For documents using the standard classes this may involve as little as adding one command at the start of the document to enable the automatic tagging. The project's GitHub page has more information. For examples with source files see here. A lot of work involves ensuring that add-on packages work with the system. The team has a package status list covering many packages.
Many TeX and LaTeX authors also have considerable interest in outputting HTML. Two examples of projects in this direction are TeX4ht and LaTeXML. Here also there has been progress on accessibility; for example see the notice at arXiv.org.
A history of reports as well as continuing updates on this work is at the LaTeX project site and on the TUG Accessibility Working Group page. (To support this progress with a financial contribution, please also see that page.)
In summary, thanks to the work of the LaTeX project, and others, TeX and LaTeX are among the leaders worldwide in providing tools that bring documents up to the latest PDF standard, and enable accessibility.