What is a .chm file?
A .chm file is a CHM document. Its registered MIME type is application/vnd.ms-htmlhelp, which places it in the application or document family of formats.
CHM stands for Compiled Help Modules.
CHM is a binary format: the contents are not readable text, so opening it in a text editor shows scrambled characters.
CHM file format details
| Extension | .chm |
|---|---|
| Format | CHM document |
| MIME type | application/vnd.ms-htmlhelp, application/x-chm |
| Category | Application or document |
| Text or binary | Binary |
| File signature | None fixed |
| Registered with IANA | Yes |
| Other extensions | None |
How to open CHM files
| Windows | CHM files (CHM document) are made by specific software. The reliable way to open one is with the program that created it; a generic viewer will only show raw data. |
|---|---|
| Mac | The same applies on a Mac: look for a Mac version of the program that makes CHM files. |
| iPhone and iPad | Phones rarely open this type of file directly. The viewer above can show what is inside it without installing anything. |
| Android | The same applies on Android. The viewer above shows the first bytes of the file so you can confirm what it is. |
Convert CHM files
TapToConvert converts CHM files in your browser, without uploading them. Open the CHM converter, or go straight to a conversion:
CHM file FAQ
What is a .chm file?
A .chm file is a CHM document, with the MIME type application/vnd.ms-htmlhelp.
How do I open a .chm file?
With the program that created it. The viewer on this page shows what is inside without installing anything.
Is a .chm file safe to open?
CHM files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .chm?
application/vnd.ms-htmlhelp, and it is also seen as application/x-chm. Web servers send this type so browsers know how to handle the file.
Is CHM a text or binary format?
Binary. Its contents are not readable as text.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.