Microsoft Active Accessibility, or MSAA for short, is a way for applications to share information about their user interface elements with access software such as screen readers. It also allows the access software to manipulate certain aspects of the user interface. It works by exposing controls as COM objects. Access software can use various functions in the COM objects to access information about the control and manipulate it.
The purpose of MSAA is to allow program authors to design custom interfaces while being able to keep their programs accessible. MSAA is built-in to some popular applications such as Microsoft Office, Internet Explorer, and Lotus Notes. There is also an effort underway to make Mozilla MSAA compliant. MSAA is also built-in to Windows 98 and above, and can be installed into Windows 95.