Adjacent focusable elements

Two elements are adjacent if all the following are true:

• both elements are included in sequential focus navigation; and
• one of the elements immediately follows the other in sequential focus navigation order; and
• there is no perceivable content between the two elements (in tree order in the flat tree).

Background

Note that if there is content that is included in the accessibility tree but not visible between both elements, then they may appear adjacent for sighted users (and notably for sighted keyboard users) but not for users of assistive technologies, and are not considered adjacent by this definition.