IAccessible

IAccessible is a COM interface that forms the core of Microsoft Active Accessibility (MSAA). It provides a programmatic bridge allowing assistive technologies, such as screen readers and magnifiers, to obtain information about and interact with user interface elements in Windows applications. By exposing UI element properties and actions through a standardized set of methods, IAccessible enables consistent navigation and interaction for users with disabilities.

The interface is implemented by user interface elements within an application and is exposed via COM/IDispatch. Key capabilities include retrieving the name, value, description, role, and state of a UI element (via get_accName, get_accValue, get_accDescription, get_accRole, get_accState), as well as information about help topics and keyboard shortcuts. It also supports hierarchical navigation (get_accParent, get_accChildCount, get_accChild), focus and selection (get_accFocus, get_accSelection), and actions such as performing the default action (accDoDefaultAction) or selecting an object (accSelect). Values can be updated with put_accValue.

MSAA and IAccessible played a central role in Windows accessibility for many years and were widely supported by early screen readers. With the introduction of UI Automation, Windows has moved toward a more capable framework, but IAccessible remains important for legacy applications and compatibility layers.

See also: Microsoft Active Accessibility, UI Automation, screen reader software.