headers attribute

The headers attribute gives authors a way to override implicit cell headers (via <th> elements) to accurately describe the structure of complex tables to assistive technology. Note: this is a difficult feature to test, as implicit headers often interfere with results. It’s not possible to tell where the header originitated from when testing with an assistive technology; is this header sourced implicitly (via <th> elements) or explicitly (via the headers attribute). Most real world tables that require the headers attribute also make use of implicit headers. Several tests are included for this feature because of this, and some of the results may be false negatives.