CHM

File Format
Name	CHM
Ontology	Electronic File Formats Help files CHM
Extension(s)	.chm
MIME Type(s)	application/vnd.ms-htmlhelp
PRONOM	fmt/634
Released	1997

CHM (Compiled HTML Help), AKA Microsoft Help 1, is a Microsoft format for help files. While it is proprietary, it has been reverse engineered, and many software applications can read it.

It is a compressed binary file format, including content in HTML as well as other related data.

Microsoft Help 2 was intended as a successor, but never saw much use.

Format description

• chmspec

Software

• chmdeco
• KchmViewer
• libmspack
• chmlib
• CHM Tools
• 7-Zip
• archmage

Sample files

• https://telparia.com/fileFormatSamples/document/chm/

Links and references

• Wikipedia article
• Ancient help-file format carries new CryptoWall attacks into PCs

See also

• Microsoft Help 2
• HLP (WinHelp)