hhctrlocx

hhctrlocx, commonly referred to as hhctrl.ocx, is the HTML Help ActiveX control used to host a HTML Help viewer inside Windows applications. It is a COM component that enables displaying CHM (Compiled HTML Help) files within a program, providing access to topics, context-sensitive help, and search functionality through the HTML Help system.

The control is part of the HTML Help Workshop runtime from Microsoft and is typically distributed with the HTML Help Workshop SDK or with software that ships CHM-based content. Developers used hhctrl.ocx to embed a CHM browser in applications created with environments such as VB6 or MFC, allowing users to navigate help topics directly within the application window.

Deployment and usage: hhctrl.ocx is implemented as a Windows DLL/OCX file that must be registered on the target system (for example, via regsvr32). It is a legacy component and may not be installed by default on newer Windows builds, which can affect applications that rely on it for help display. When present, the control works in tandem with the HtmlHelp API to render and navigate HTML Help content.

Security and lifecycle: As an ActiveX control, hhctrl.ocx has historically carried security considerations and potential vulnerabilities associated with older COM-based components. Modern development often favors newer help systems or web-based documentation, and if CHM-based help is required, developers typically ensure the runtime is obtained from trusted sources and kept up to date. In contemporary contexts, many applications migrate away from hhctrl.ocx in favor of alternative documentation approaches.

See also: CHM, HTML Help, HtmlHelp API, ActiveX, regsvr32.