Note:

In WCAG 2.2, success criterion 4.1.1 Parsing is designated as "obsolete and removed." Versions 2.1 and 2.0 of WCAG now include this note concerning conformance with 4.1.1 Parsing:

"This Success Criterion should be considered as always satisfied for any content using HTML or XML."

See the WCAG 2 FAQ for the reasoning behind the obsoletion of this criterion.