HowtoMatrix

Microsoft Compiled HTML Help is a proprietary format for online help files, developed by Microsoft and first released in 1997 as a successor to the Microsoft WinHelp format. It was first introduced with the release of Windows 98, and is still supported and distributed through Windows XP platforms.

HTML Help files are made with help authoring tools. Microsoft ships the HTML Help Workshop with supported versions of Microsoft Windows and makes the tool available for free download. There are also a lot of third-party help authoring tools available.

CHM files, known as Microsoft Compressed HTML Help files, are a common format for eBooks and online documentation. They are basically a collection of HTML files stored in a compressed archive with the added benefit of an index.

Under Linux, you can view a CHM file with the xchm viewer. But sometimes that’s not enough. Suppose you want to edit, republish, or convert the CHM file into another format such as the Plucker eBook format for viewing on your Palm. To do so, you first need to extract the original HTML files from the CHM archive.

This can be done with the CHMLIB (CHM library) and its included helper application extract_chmLib.

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