CHM Document — A .chm file is a CHM Document. It is a document format used for word processing, spreadsheets, presentations or ebooks.
Quick facts
What is .chm
A .chm file is a CHM Document. It is a document format used for word processing, spreadsheets, presentations or ebooks.
In the mime-db registry it maps to application/vnd.ms-htmlhelp. When serving .chm over HTTP, set the Content-Type header as shown in Developer info below.
Related entities: it maps to application/vnd.ms-htmlhelp — and is delivered over HTTP via the Content-Type header.
How to open .chm files
Developer info
When served over HTTP, responses should set the following header:
Content-Type: application/vnd.ms-htmlhelp
Common software that reads/writes .chm:
Relation chain
Related extensions
Related MIME types
Common uses
How to edit .chm files
How to create .chm files
Frequently asked questions
Common options include Microsoft 365, LibreOffice, Adobe Acrobat. You can also open many of these files with built-in viewers or a browser.
Create a new file in any text editor or the app that owns the format and save it with the .chm extension.
application/vnd.ms-htmlhelp is the media type identifier used for .chm files during network transfer (for example in the HTTP Content-Type header).
Sources & standards
Updated 2026-08-18
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