How to Decompile Windows chm Help Files

We show how to decompile a Microsoft HTML Help file with chm extension using the hh.exe onboard Windows tool.

Microsoft Compiled HTML Help is a proprietary online help format invented by Microsoft and released August 1997 with Internet Explorer 4. It is still used and supported up to Windows’ latest Version 7.

These help files come with a .chm file extension. They contain a set of HTML files, a TOC (table of contents) and an index file. The files start with the identifier “ITSF” which is an acronym for Info-Tech Storage Format. chm files can easily be produced with a variety of programs, e.g. with HTML Help Workshop.

If you happen to be in need of a decompiled version of a specific chm file, you will find several paid solutions on the Internet that claim to do the job. But there is no need to spend money since Windows is shipped with a program called hh.exe that is not only used to display help files but also suitable for decompiling chm files.

Follow these simple steps to decompile a chm file:

1. Open a command prompt by pressing Win+R and entering cmd.exe followed by pressing <Return>.
2. Change to the folder with your chm file using the cd command, e.g.
   c:> cd c:HelpFiles.
3. Now use the hh command to decompile:
   c:HelpFiles> hh -decompile <TargetFolder> <MyFile>.chm

The process will finish quickly and you will find your decompiled chm parts in the <TargetFolder> directory.