A web page must meet the WCAG 2.1 success criteria under guideline 3.1 (readable): 3.1.1 language of page and 3.1.2 language of parts. Each numbered sub-clause of 9.3.1 requires one criterion, in the same order as WCAG.
This control maps to 1 controls across 1 other frameworks. If you already hold one of them, the evidence you collected for it is the starting point here rather than new work.
Every mapping shown was judged rather than inferred from wording similarity, and the ones that failed review are published too. See the coverage reports and what was rejected.
The graph holds this control, the 1 it maps to, and the evidence behind each claim, over MCP and REST.