Filename extension .chm Initial release 1997 Extended to .lit | Latest release 1.4 | |
Internet media type application/vnd.ms-htmlhelp | ||
Microsoft Compiled HTML Help is a Microsoft proprietary online help format, consisting of a collection of HTML pages, an index and other navigation tools. The files are compressed and deployed in a binary format with the extension .CHM, for Compiled HTML. The format is often used for software documentation.
Contents
It was introduced as the successor to Microsoft WinHelp with the release of Windows 98 and is still supported in Windows 7. Although the format was designed by Microsoft, it has been successfully reverse-engineered and is now supported in many document viewer applications.
History
Microsoft has announced that they do not intend to add any new features to HTML Help.
File format
Help is delivered as a binary file with the .chm extension. It contains a set of HTML files, a hyperlinked table of contents, and an index file. The file format has been reverse-engineered and documentation of it is freely available.
The file starts with bytes "ITSF" (in ASCII), for "Info-Tech Storage Format".
CHM files support the following features:
Use in Windows applications
The Microsoft Reader's .lit file format is a modification of the HTML Help CHM format. CHM files are sometimes used for e-books.
Sumatra PDF supports viewing CHM documents since version 1.9.
Various applications, such as HTML Help Workshop and 7-Zip can decompile CHM files. The hh.exe utility on Windows and the extract_chmLib utility (a component of chmlib) on Linux can also decompile CHM files.
The Free Pascal project has a compiler (chmcmd) that can create CHM files in a multiplatform way.
Use in non-Windows applications
Read support:
Read/write support: