Apple includes a few tools with macOS to help manage unnecessary files on your computer.
On the Storage screen, you should see a graphic showing your drive’s available space. Click the Manage button on the right side of the box to get started. The resulting storage-management screen offers four ways to clear off old files: Store in iCloud, Optimize Storage, Empty Trash Automatically and Reduce Clutter.
As one might expect, the Store in iCloud option punts documents, photosand Messages off your Mac’s drive and into your iCloud online storage locker. While this does free up room on the computer, you may have to buy more iCloud storage space from Apple if you fill up your five gigabytes that come free with an iCloud account.
Enabling the Optimize Storage feature dumps iTunes videos you have already watched, but you can download them again later. The setting also changes the Mail program’s behavior regarding file attachments to retrieve only recent files — or only those that came with messages you have opened.
The Empty Trash Automatically setting permanently deletes files that have been living in the Mac’s trash for longer than 30 days. (In macOS Sierra and later, the system also automatically dumps duplicate Safari downloads, cache files, logs and other unneeded files.)
Using the Reduce Clutter feature is another way to find big files hogging drive space and remove them. To see what the Mac considers “clutter,” click the Review Files button and go through the lists of files deemed large, old or unnecessary. Click the X next to each file to delete it.
If you are running a version of the operating system older than macOS Sierra, you can manually wade through your drive tossing old files or get a third-party cleaning app to sweep up for you. The Macworld site has a detailed list of cleaning tips that explains how to find and trash old Mail downloads, cache files and disk images.
If you’d rather have software do the job, a combination of MacPaw’s CleanMyMac 3 and Gemini 2 (for system cleaning and duplicate-file removal) is an option; free trials of the programs are available. Disk Cleanup Pro and Dr. Cleaner are among the free utilities in the Mac App Store, and others can be found online. As with all maintenance programs, however, read the reviews before you download and back up your Mac before using software intended to automatically delete files on your computer — just in case.