Browser Helper Object

A plugin module for web browsers (originally Internet Explorer) that loads with each browser instance and has access to the Document Object Model and browser events. In accessibility contexts, BHOs have been used to implement client-side web page transformations such as text enlargement, color changes, page linearization, and text-to-speech, modifying pages after they are rendered without requiring changes to the original web content or a proxy intermediary. While BHOs were specific to Internet Explorer, the concept evolved into modern browser extensions that serve similar accessibility adaptation purposes.