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What is the .CHM File Extension?

.CHM File Extension Description:

The Compiled HTML Help (CHM) was developed in 1997 as a successor to Microsoft WinHelp and introduced with the release of Windows 98. It is still distributed through Windows XP and Vista. The CHM help files use the CHM file extension.

The files with the .chm file extension are made with the Microsoft help authoring tools. These files are set of web pages written in a subset of HTML and hyperlinked table of contents. They are heavily indexed, thus they are optimized for reading. CHM browsers outside of the body text of the help file display files with the .chm file extension.

The CHM file extension starts with bytes in ITSF (InfoTech Storage Format), which has been reverse engineered partially along with the internal files and the container. The CHM file extension format was originally intended for encoding help files, however, it has been a very handy tool for packing and browsing saved HTML pages in one compact archive. Some people to keep personal notes because of its ability to organize them in hierarchical order also use it.

The file with the .chm file extension is smaller in size than plain HTML. It contains a variety of HTML formatting options used for text presentation. It is also capable of generating Table of Contents and Topic Folders that contain standard international characters, which standard HTML Help is not capable of.

On Windows, the CHM file extension can be extracted to plain HTML using the hh.exe command decompressing all the files embedded in it to the folder extracted or by using the HTML Help Workshop. On Linux, the file with the .chm extension can be decompiled by using apt as an actual packaging tool. In non-Windows environment, the CHM Tools Package that includes a source code and a program called CHMDUMP is used for extracting CHM files into separate directory.

Other applications can read and explore files with the .chm file extension such as xCHM, KchmViewer, GnoCHM, and Chmox for OS X, Chamomix for OS X, Firefox add-on CHM Reader or the Help Explorer Viewer.

Author: Microsoft Corporation
Author URL:
Related Applications: Microsoft Help authoring tools
Common Path: C:/ Windows


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Do you have errors with .CHM files?

What Causes .CHM files Errors to Occur?

.CHM files errors are possibly severe Windows file system errors and may be brought on due to a broken program registry that you should fix immediately to avoid further failure in other software and/or devices. While the errors persist your system stays capable of potential blue screen errors, system failure and fatal crashes.

What are the Symptoms of .CHM files Errors?

Common symptoms with .CHM files errors include reduced computer speed, long application load speed, trouble saving documents, extended suspensions in program routines, software closes without an error, input freezes and applications lock up.

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