Its invalid-extension tool can flag mismatches between content signatures and filenames for some formats. It cannot reliably identify every custom file type.
What to know before you begin
Its invalid-extension tool can flag mismatches between content signatures and filenames for some formats. It cannot reliably identify every custom file type. The project offers several scanning modes and the current version may place controls differently in Krokiet versus the older GTK GUI. Follow the meaning of the option you see, not just a screenshot from a different release.
For Windows, verify that your chosen folder is accessible and that the correct graphical frontend is running. The recommended approach starts with a small test set, especially when an action could rename, move, delete or link files.
Step-by-step: Can Czkawka detect wrong file extensions?
- Run the invalid-extensions mode on a sample folder.
- Check flagged files against a trusted application.
- Rename only files with confirmed correct content.
- Recheck application associations after changes.
Important limitation
How to verify the result
Verify renamed files open in the intended application. A scan's estimated savings or the presence of a matching group does not by itself establish which copy should be discarded.
If the procedure does not match your screen, inspect the project's own FAQ and troubleshooting notes and identify the exact release and frontend first.
FAQ
Can Czkawka detect wrong file extensions?
Its invalid-extension tool can flag mismatches between content signatures and filenames for some formats. It cannot reliably identify every custom file type.
What is the biggest risk for this task?
A valid proprietary file can be mislabeled by generic signature detection.
How do I check whether it worked?
Verify renamed files open in the intended application.
Related Windows guides
- Czkawka Broken Files Scan: What It Can and Cannot Tell You
- Remove Empty Folders with Czkawka Safely
- Find Empty Files in Windows with Czkawka
- Find Large Files and Disk Space Hogs
Editorial notes reviewed: November 1, 2026. Version-specific facts are based on the developer's release and FAQ. This guide is educational; it is not a guarantee about a third-party download.
Try Czkawka on Windows
Check the asset name and keep a backup before running a file cleanup operation.
See our download and safety instructions first.