Widget index / Basic controls · Download this HTML
Ready — try the example.
States and behavior
Unchecked, checked, mixed aggregate, focused, disabled checked.
Keyboard
Tab visits each enabled checkbox; Space toggles. Activating a mixed parent selects all children.
Scope and adaptation
Mixed describes an aggregate, not a third saved boolean. Setting indeterminate is separate from checked.
Sources
Microsoft preliminary guide (1995), chapters 7–8 · Modern browser accessibility pattern
Original implementation; system colors are represented by CSS variables. The default 13 px system-font stack is a readable browser adaptation. The 1995 source is preliminary, not a final product specification. Test the target browser and native host before shipping.