Use Disk Cleanup
Free Up Space on MacBook Air or MacBook Pro (12 Easy Ways)
Encrypt Mac data with FileVault
Delete unneeded media, such as music or movies or podcasts, which can use a lot of storage space. Delete unneeded files in the Downloads folder. You can open the Downloads folder from the Dock or by choosing Go > Downloads from the menu bar in the Finder. Delete unneeded email in the Mail app.
Everything you need in an optical drive. Whether you're at the office or on the road, you can play and burn both CDs and DVDs with the Apple USB SuperDrive. It's perfect when you want to watch a DVD movie, install software, create backup discs, and more.
Change your startup disk for every startup On your Mac, choose Apple menu > System Preferences, then click Startup Disk . If the lock at the bottom left is locked , click it to unlock the preference pane. Click the icon of the disk you want to use, then click Restart.
How to select a startup disk on Mac
How to free up disk space on Mac using compression?
Delete the Safari cache Near the middle of the menu, you'll see an Empty Caches menu item. Select this, and Safari will delete the files it's stored on your Mac. This will help free up some disk space; some cases, there can be hundreds of megabytes of files, or even more.
It depends on the intended usage of the drive, but in general 20% to 15% free space is a good answer for spinning disks, and 10% or more is good for SSDs. If this is the main drive on the computer and files may be moved, then 20% free space should prevent significant slowdowns.
See used and available storage space on your Mac
What is FileVault? FileVault full-disk encryption is a tool in your macOS that helps you protect data on your startup disk. FileVault full-disk encryption, or FileVault 2, provides full-disk XTS-AES-128 encryption with a 256-bit key. It's easy to set up on your device and helps protect your files from unwanted access.
A. For years, Mac computers did not come with utilities like Disk Cleanup and the newer Storage Sense found in Windows, but Apple added new tools in 2016 with the release of its macOS Sierra system.