HLP

hlp is a filename extension associated with Windows Help files produced by the WinHelp system. These compiled help files were used to provide software documentation and context-sensitive assistance within Windows applications. A typical .hlp file contains a collection of topics, a contents or table of contents, an index, and a search function, all interconnected through topic IDs and hyperlinks.

The content behind an .hlp file is usually created from source materials written in rich text or plain text and organized with project files produced by the Microsoft Help Workshop. The compiled file bundles text, images, and navigation structures into a single binary used by the Windows Help runtime. Users navigate through topics via a contents pane, an index, or a search interface, with links enabling cross-referencing between topics.

WinHelp, the original toolchain for .hlp files, gained prominence in the 1990s and remained common through the Windows 9x era. Microsoft gradually shifted to the HTML Help system, which produced .chm files, as a more flexible and web-like format. As a result, .hlp files are now largely considered legacy documents. In modern Windows versions, viewing .hlp files typically requires legacy support packages such as a WinHlp32.exe viewer or third-party applications, since native support has waned.

Today, .hlp files are mostly found in older software distributions and archival collections. They are superseded in new software by HTML Help (.chm) or online documentation, but they remain a notable example of early digital help systems and software documentation workflows.