clean up, back up
Lose files you don’t need and safeguard the ones you do
Keeping old files won’t slow down your Mac; it just ignores them. But you’ll have problems if your drive gets close to full. Automatic defragmentation will start to struggle, macOS may not have room to swap data while multitasking and apps that use ‘scratch disk’ space will run out. You’ll need a few extra gigabytes to download and install Catalina, so it’s a good time to make room.
Use a Finder search (see ‘Find and delete large files’, below) to isolate the biggest files you no longer need. This doesn’t work for folders, because their size isn’t automatically calculated, and forcing the Finder to do so will take ages. Large folders of small files would typically be temporary files belonging to an app. For example, video-editing apps save render files so your timeline plays
smoothly, but you can delete those for old projects – you’ll just have to wait for re-rendering if you go back and edit them. Search online for advice on where your favourite apps keep their temp files and which can safely be deleted.
Get backed up
Time Machine is the easiest way to back up your Mac. You’ll need an external drive bigger than the contents of your internal storage plus any connected drives that you want backed up. You will then be able to retrieve individual files, or restore your whole system: see bit.ly/ mf343rstr for how to do that.
Some network-attached storage (NAS) boxes are compatible with Time Machine and can be selected as a backup drive as long as they’re on the same network as your Mac. Note that Time Machine can only back up one set of locations to one drive; if your needs are more complicated, consider a third-party backup or cloning app. Alternatively, you can make a one-off clone of a drive using macOS’ Disk Utility, although if it’s your startup drive you’ll first need to restart from Recovery: see bit.ly/mf343rcvr. Another option is an online backup service, such as Backblaze (backblaze. com) or iDrive (idrive.com)