A few minutes of preparation makes cleanup results easier to understand and reduces the chance of interrupting work that is still using temporary data.
Save and finish active work
Save open documents and finish file copies, exports, installations, and system updates. An application can create, rename, or lock files while a scan is running, which can make results stale or cause a removal to be skipped.
Quit applications related to the category you intend to clean. For example, quit Mail before removing cached attachments and quit an application before uninstalling it.
Make a current backup
Use Time Machine or another backup system for irreplaceable documents, photos, projects, and settings. Confirm that the latest backup completed successfully and that its destination is available.
A scan is not a backup. Cleanup history records supported operations but does not contain copies of removed files.
Connect required storage
Mount the external disk or network location you intend to analyze. Keep it connected until scanning and any confirmed operation finish.
Disconnect unrelated removable disks if doing so makes it easier to avoid selecting the wrong location.
Check available power and time
Connect a Mac notebook to power before scanning a large disk or comparing many files. Prevent sleep if an unattended scan would otherwise be interrupted.
Start with a small, familiar folder when learning a new tool. You can expand the scope after you understand its result layout.
Review permissions
Do not enable every permission automatically. Open the tool you want to use, read its explanation, and grant the access required for that location.
After changing Full Disk Access, quit and reopen diCleaner before rescanning.
Establish a safe first target
Choose generated data you recognize, not personal files selected only because they are large. Expand every category, deselect uncertain items, and remove a small batch first.
After the operation, reopen affected applications and verify that normal work continues before cleaning more.