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|Internet media type|
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|Internet media type|
|A component of Microsoft Windows|
|Included with||Windows 98|
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.
|February||1996||Microsoft announces plans to stop development of WinHelp and start development on HTML Help.|
|August||1997||HTML Help 1.0 (HH 1.0) is released with Internet Explorer 4.|
|February||1998||HTML Help 1.1a ships with Windows 98.|
|January||2000||HTML Help 1.3 ships with Windows 2000.|
|July||HTML Help 1.32 releases with Internet Explorer 5.5 and Windows Me.|
|October||2001||HTML Help 1.33 releases with Internet Explorer 6 and Windows XP.|
|March||At the WritersUA (formerly WinWriters) conference, Microsoft announces plans for a new help platform, Help 2, which is also HTML based.|
|January||2003||Microsoft decides not to release Microsoft Help 2 as a general Help platform.|
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:
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.