Microsoft Compiled HTML Help (CHM) 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. The format was intended to succeed Microsoft WinHelp.
Although the format was designed by Microsoft, it has been successfully reverse-engineered and is now supported by many document viewers.
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.[6]
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.[7][8]
The file starts with bytes "ITSF" (in ASCII), for "Info-Tech Storage Format", which is the internal name given by Microsoft to the generic storage file format used for CHM files.[9]
Microsoft's HTML Help Workshop generates CHM files by instructions stored in a HTML Help project file, which bears a .HHPfile name extension and is a specialized form of INI file.[12]
The official viewer in Microsoft Windows (hh.exe) can decompile a CHM file. So can Microsoft HTML Help Workshop and 7-Zip. Calibre and arCHMage can convert CHM into another format.
