How to open .CLS files on Windows
To open .CLS files on Windows, right-click the .cls file and choose open with..
Step-by-step instructions
- Right-click the .CLS file and choose Open with.
- Select a trusted Windows app that supports .CLS files.
Recommended software
- Microsoft 365
- LibreOffice
- Google Docs (web)
Alternative methods
- Open .CLS in a browser-based viewer if desktop apps fail.
- Try opening .CLS on Windows with a secondary app to rule out app-specific issues.
- Convert .CLS only with trusted tools when direct opening is not possible.
Common issues
.CLS file does not open
This usually means the required app is missing or the .CLS file is incomplete.
- Install or update a compatible application.
- Verify the file came from a trusted source and was fully downloaded.
- Try opening the file in an alternative app on another platform.
Security note
Only open .CLS files from trusted senders.