How to clean the MAC Pro Hard Drive

• empty trash

• connect your backup drive and allow it to compete a copy to the drive, which frees up temporary backup snapshots on the boot drive. If you do not have a local, disk-based backup, we need to talk more about that.

• delete everything in the Downloads folder. all those files came from the Internet. if needed, they can be downloaded again later.

• obtain an additional drive, and copy less frequently used items orally big items like your photos library to it.

More ideas here, but remember that storing files on iCloud can be an addiction, and there is almost no way back except to obtain more drives (which is likely what you need in the first place).

Free up storage space on Mac - Apple Support

If your Mac Pro’s hard drive is showing that a huge chunk of space—like 175 GB—is being taken up by “System Data,” don’t worry, that’s pretty common, and you can clean it up with a few practical steps. First, restart your Mac; sometimes, cached files and temporary data get cleared just by doing that. Next, go to Apple Menu > About This Mac > Storage > Manage and look through the recommendations—use the “Reduce Clutter” and “Empty Trash Automatically” options. Then, clear out your cache files by opening Finder, clicking Go > Go to Folder, and typing ~/Library/Caches. You can delete everything inside the folders (not the folders themselves).

Also, check your Downloads folder and old iOS backups in Finder > Go > Go to Folder > ~/Library/Application Support/MobileSync/Backup. If you’re using Final Cut, GarageBand, or Logic, check for unused media or old project files that pile up fast. And if “System Data” is still massive, it may include Time Machine snapshots, open Terminal and type tmutil listlocalsnapshots /, then delete old ones using sudo tmutil deletelocalsnapshots [snapshotname].

Just make sure you back up your data before deleting anything deep in the system.