aria-checked
Widget attributes might be mapped by a user agent to platform accessibility API state, for access by assistive technologies, or they might be accessed directly from the DOM. User agents MUST provide a way for assistive technologies to be notified when states change, either through DOM attribute change events or platform accessibility API events.
Indicates the current "checked" state of checkboxes, radio buttons, and other widgets. See related aria-pressed and aria-selected.
The aria-checked attribute indicates whether the element is checked (true), unchecked (false), or represents a group of other elements that have a mixture of checked and unchecked values (mixed). Most inputs only support values of true and false, but the mixed value is supported by certain tri-state inputs such as a checkbox or menuitemcheckbox.
The mixed value is not supported on radio, menuitemradio, switch or any element that inherits from these in the taxonomy, and user agents MUST treat a mixed value as equivalent to false for those roles.