CLS File Extension
LaTeX Document Class Format
- File Type cls
- Popularity
- Application Sublime Text
- Category Developer Files
- Format Text
What is a CLS file?
LaTeX Document Class Format, identified by the CLS extension, is a Developer Files type and includes 1166 files.
CLS files are supported by Windows, Linux and Mac OS. You can open a CLS file using one of 4 programs, for example Sublime Text, Atom and PSPad.
Programs that support CLS files
How to open a CLS file?
The most common reason why a CLS file cannot be opened is the absence of required software. To fix this, select a compatible program from the list. Then visit the official developer website via the provided link, download the program, and install it on your system.
The most popular programs for working with CLS files are Sublime Text, Atom and PSPad. To get the latest version of Sublime Text, open the Sublime HQ Pty website where a universal installer for all operating systems is available.
Once setup is done, your operating system should assign Sublime Text as the default app for CLS files.
Make Sublime Text the default CLS viewer
Changing the default program in Windows
- Start by right-clicking on your CLS file and selecting the "Open With" option. From there, click "Choose another app" to continue;
- Inside the popup window, scroll through the list of applications and specifically choose Sublime Text as the application to associate with your CLS file;
- Check the "Always use this app" checkbox and click "OK".
Change the default app to open files on Mac
- Right click or use Control + Left Click on the desired CLS file to access a dropdown menu of actions;
- Select "Open in application" and click "Other";
- Scroll down to the bottom of the window, where you will find the "Enable" menu. Default, "Recommended Programs" will be selected;
- In this menu, choose "All Programs" and navigate to Sublime Text. Check the box next to "Always open in app" to make it the default program.
How to edit a CLS file?
To edit CLS files, you need to install specialized software that allows you not only to open but also to modify developer files. Online CLS editors usually provide fewer features than software created specifically for LaTeX Document Class Format.
List of Top CLS editors 2026
Following these criteria, we have put together a list of recommended CLS editors.
| CLS Editor Software | Developer | Platforms | Overall Rating |
|---|---|---|---|
| Sublime Text | Sublime HQ Pty | Windows, Mac OS, Linux | 4.8 out of 5 (42 reviews) |
| PSPad | Jan Fiala | Windows | 4.4 out of 5 (43 reviews) |
| Atom | - | Windows, Mac OS, Linux | 4.3 out of 5 (39 reviews) |
| Notepad++ | Notepad++ Team | Windows | 4.1 out of 5 (40 reviews) |
Finding answers to CLS file problems
If you encounter issues with CLS files, don’t worry—most can be fixed with minor software adjustments. Refer to the troubleshooting tips below.
What are the signs that my CLS file is damaged?
Corrupted CLS developer files may have one or more of the following symptoms:
- Poor performance when editing a file in Sublime Text;
- Opening or processing the file in Sublime Text or other programs causes instability or crashes in the program;
- The file shows errors when trying to open it or does not open completely;
- Unexpected expansion of the total size of the CLS file;
- Working with the file triggers the display of error messages;
Why does Sublime Text quit or crash unexpectedly?
Sublime Text crashes can be attributed to outdated software. Make sure you have installed the latest updates for Sublime HQ Pty products.
A computer restart is often the key to solving numerous common problems. That’s why, it is recommended to restart the computer before making any changes to the software settings.
What methods can be used to repair a damaged CLS file?
Use a recovery program to open the damaged CLS file and navigate to the "Repair" menu item. Wait for the recovery process to finish, as it will automatically repair damaged developer files.