File Extension CHM

.CHM File

File extension: CHM
File type: Compiled Help File


Notes about the CHM file extension:



To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened" (Windows 7) or "How do you want to open this file?" (Windows 10) if you double-click the file. There click on "More apps" and choose a suitable software to view such files on your PC or from email attachments.

The CHM file type is primarily associated with 'HTML Help' by Microsoft Corporation. Used by HTML Help 1.x. Note: This file type can become infected and should be carefully scanned if someone sends you a file with this extension. The starting characters, ITSF, stands for InfoTech Storage File; Microsoft's name for the library that reads/writes .CHM files.

Detailed information for file extension CHM:


Primary association: HTML Help
Company: Microsoft Corporation
Identifying characters Hex: 49 54 53 46 , ASCII: ITSF
Program ID: chm.file
Related links: Info Page, Unofficial (Preliminary) HTML Help Specification, Unpack with 7-Zip

Other applications associated with file type CHM:

  • Ares Font Chameleon (Source Font - Font Outline)
  • ChemDraw (Chemical Structure) by CambridgeSoft CorporationOld format. The Mime types used with this association are: chemical/x-chemdraw, application/x-chemdraw.
File Identifier - TrID
'Identifying characters' used on FILExt.com are
provided by Marco Pontello from his TrID database




To change file associations press Windows Key + X and then Apps and Features > Default apps > Choose default apps by file type. Invalid file associations could be the result of underlying issues within your Windows PC.

Technical data

To view technical data on file-extension CHM click this link to expand/hide the additional area.

System Info for File Extension .CHM

The following listing is compiled from the database produced by the 'Associate This!' program, selected data from the main FILExt database and information FILExt collected directly from user systems.

ProgramID: chm.file, FileType: Compiled HTML Help file, AppName: Microsoft® HTML Help Executable
EXEFile: hh.exe

ProgramID: chm.file
EXEFile: %SystemRoot%\hh.exe %1

ProgramID: chm.file
EXEFile: %SystemRoot%\ServicePackFiles\i386\hh.exe %1

ProgramID: chm.file
EXEFile: %SystemRoot%\system32\notepad.exe %1

ProgramID: chm.file
EXEFile: %SystemRoot%2\hh.exe %1

ProgramID: chm.file
EXEFile: D:\WINXP\hh.exe %1

ProgramID: chm.file
EXEFile: C:\WINXP\hh.exe %1

ProgramID: chm.file
EXEFile: %SystemRoot%.1\hh.exe

ProgramID: chm.file
EXEFile: %SystemRoot%1\hh.exe

ProgramID: chm.file
EXEFile: %SystemRoot%C\hh.exe


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