Block files: Audacity stores the audio data in multiple short sections or block files (normally six seconds long). For details please see
Structure of an Audacity project.
This warning message will be shown when you attempt to open an Audacity project which has audio data which does not appear in any of the tracks in the project.
The warning dialog in project context

Your options
You have three options offered to you at this stage:
- Continue without deleting; ignore the extra files this session (default):
- Choosing this default option will cause Audacity to ignore the orphan files.
- The orphan files will be saved if and when you subsequently Save the project, so the next time you Open the project you will get this message again.
- Close project immediately with no further changes):
- Choosing this option will cause Audacity to abandon the opening of the project.
- Audacity will leave your data exactly as it was prior to you attempting to open the project.
- Delete orphan files (permanent immediately):
- If you choose this option Audacity will immediately and permanently delete all the orphan block files.
- The next time you open the project you should no longer see this warning, Audacity will just open the project.
Once you have made your choice, simply click on the OK button.
The Log file
If you want to see further details of the orphan block files click on the Show log for details button.
