CHM File Extension
Compiled HTML Help Format
- File Type chm
- Developer Microsoft
- Popularity
- Application Microsoft HTML Help Workshop
- Category Blocked Email Attachment Files, Dangerous Files, Document Files
- Format Binary
What is a CHM file?
Files with the CHM extension are associated with Compiled HTML Help Format and are categorized as Blocked Email Attachment Files, Dangerous Files and Document Files, making up 1131 files.
The Compiled HTML Help Format (CHM), created by Microsoft, is one of file format they developed, and they also built 242 programs to support them.
CHM files are compatible with various operating systems, including Windows, Linux and Mac OS. When working with CHM files, you can rely on 9 programs, including Microsoft HTML Help Workshop, xCHM and Microsoft Windows.
File Signature
HEX code: 49 54 53 46. ASCII code: ITSF.
Programs that support CHM files
How to open a CHM file?
If you can’t open a CHM file, it is usually because the necessary software is missing. To resolve the issue, select the right program from the list for your operating system. Then go to the official website of the developer, download the software, and install it.
Microsoft HTML Help Workshop, xCHM and Microsoft Windows are among the most widely used programs for handling CHM files. To install the most up-to-date edition of Microsoft HTML Help Workshop, visit the official Microsoft website. You can download the build that works across all operating systems.
After installing, your OS should instantly open CHM files with Microsoft HTML Help Workshop.
Setting Microsoft HTML Help Workshop as default CHM viewer
Change the default app for a file type in Mac
- Initiate a right click or use Control + left click on the desired CHM file to open a menu where you can select various actions;
- Choose "Open in Application" and click "Other";
- Look towards the bottom of the window, where you will find the "Enable" menu. "Recommended programs" will be the default selection;
- Choose "All Programs" in this menu and search for Microsoft HTML Help Workshop. Check the box next to "Always open in app" to set it as the default option.
Change default programs in Windows
- Take the first step by right-clicking on your CHM file. Next, select "Open With" and then choose "Choose another app" from the available options;
- Choose Microsoft HTML Help Workshop from the available applications listed in the pop-up window to set it as the default application to open your CHM file;
- Be sure to check the "Always use this app" checkbox, and then click "OK" to confirm your selection.
Tips and tricks to solve problems with CHM files
Problematic CHM files can usually be resolved by making small changes in your software. See the tips below to help fix common issues.
Are there any techniques or tools available to repair a damaged CHM file?
In a data recovery program, open the damaged CHM file and select the "Repair" menu option. Wait for the recovery process to finish as it will automatically restore the damaged blocked email attachment files.
How do I know if my CHM file has been damaged?
The signs of corrupted CHM blocked email attachment files can manifest as:
- Error alerts occur when actions are performed on the file;
- The file shows slow performance when edited in Microsoft HTML Help Workshop;
- The file encounters problems during the opening process or shows error indications;
- An unexplained increase in the size of the CHM file;
- The file causes Microsoft HTML Help Workshop or other software to hang or crash during various operations;
What factors contribute to Microsoft HTML Help Workshop crash?
Lack of software updates is a possible reason behind Microsoft HTML Help Workshop crash. Keep your Microsoft products up to date by installing the latest updates.
Restarting your computer is an essential troubleshooting step that can resolve many common problems. It is recommended to restart your computer before making any changes to the software settings.
How to edit a CHM file?
To modify CHM files, it is necessary to install dedicated software that lets you open and edit blocked email attachment files. Online CHM editors generally offer fewer tools compared to programs designed for Compiled HTML Help Format.
Best CHM editors 2026
Based on the specified criteria, here is a list of CHM editors that may fit your requirements.
| CHM Editor Software | Developer | Platforms | Overall Rating |
|---|---|---|---|
| Microsoft HTML Help Workshop | Microsoft | Windows | 4.4 out of 5 (42 reviews) |