CHM - Compiled HTML Help File

What is a CHM file

CHM (Microsoft Compiled HTML Help) files fall under Microsofts proprietary files. They consist of HTML pages used for online help formatting and indexing of navigation tools. CHM files are compressed and deployed using binary formats and often used for software documentation. The first release of CHM files followed Windows 98 with continued support throughout other Windows versions. Compatibility with web browsers (regardless of computer) is the strongest point for this file, while the weakest link falls in the ability for certain controls to be executed by the CHM files, leading to problems.

CHM files are found within the help files of Windows, replacing Microsoft WinHelp. Within the HTML pages and index, 28 different language types can be supported. Compression, merging, and searching is possible within the document. Tags, images, text, hyperlinks, and more can be included in the HTML pages to improve the quality of the help files. Due to reverse engineering, CHM files are supported in various document viewer programs and applications. The LIT file extension is a modified form of the CHM file since CHM files are capable of being used for eBooks as well. Despite the lack of support for Unicode, many other extended characters are supported. Compression is accomplished using LZX compression but can be decompressed using the HTML Help Workshop and 7-Zip.

Here's a small, but not exhaustive list of programs that can open CHM documents:

  • Beyond CHM
  • Microsoft Internet Explorer
  • Microsoft Reader
  • Mozilla Firefox
  • xCHM