Microsoft Compressed HTML Help
| Filename extension | .chm |
|---|---|
| Internet media type | application/vnd.ms-htmlhelp |
| Developed by | Microsoft |
| Initial release | 1997 |
| Latest release |
1.4
|
| Extended to | .lit |
| A component of Microsoft Windows | |
|---|---|
| Details | |
| Type | Help system |
| Included with | Windows 98 |
| Replaces | Microsoft WinHelp |
| Replaced by | Microsoft Help 2 |
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.
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.
Microsoft has announced that they do not intend to add any new features to HTML Help.
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:
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.
Read support:
Read/write support:
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