Because of the relatively high cost of SSD storage, when buying a new Mac you might choose to pick a smaller-capacity drive than in a Mac you’re replacing. That might be to reduce the overall expense or to spend your budget on more RAM or a faster processor. Apple still offers laptops with 256GB SSDs, and that seems a little snug if you have digital downloads or ripped music and take even a modest amount of photos and videos.
iCloud is a solution for offloading on-device storage and offers a kind of loose backup of that material, too. In the US, you can upgrade iCloud storage from the included 5GB to 200GB for $ 2.99 per month and 2TB for $ 9.99 per month.
Here’s a strategy for migration, if you’re comfortable with many of your files having the only copy living in iCloud.
Enable iCloud Photos in Photos
In Photos, choose Photos > Preferences > iCloud. Check the iCloud Photos box and then select Optimize Mac Storage. If iCloud Photos was already enabled, macOS will only for sure retain thumbnails of images and videos. However, if you’re turning it on for the first time, Photos will upload all locally stored images. After those are copied to iCloud storage, Photos can optionally delete any local version and just show a thumbnail.
For a large Photos library, this can restore nearly all the space occupied by the library. Photos and videos are downloaded on demand as you view or use them.
Optimize iCloud Drive storage
In the Apple ID preference pane’s iCloud view (Catalina) or the iCloud preference pane (Mojave and earlier), there’s a checkbox marked Optimized Mac Storage. If it’s selected, macOS removes the least-accessed files from your local synced copy of iCloud Drive as your computer’s available storage drops; these files remain available in your online iCloud storage.
A sort of shadow version remains available on your desktop, so you can see the file and search against it. If you try to open that file, macOS quietly retrieves it from your iCloud account to make it available.
Enable Desktop & Documents Folders in iCloud Drive
Outside of images, your videos, and locally stored music, your Documents folder can occupy the most space. Some people organize on their Desktop, making it necessary to link both. With this item checked in iCloud Drive’s Options, macOS syncs the contents with iCloud Drive. But with the Optimized Mac Storage box checked as well, your Desktop and Documents folders are removed as necessary to make room on local storage after being uploaded.
iCloud Music Library via Apple Music or iTunes Match
With a subscription to the Apple Music service (various prices) or iTunes Match ($ 24.99 per year), you can use iCloud Music Library to sync music files you have downloaded on your Mac to iCloud. This doesn’t count against your iCloud storage, interestingly enough. Locally downloaded music and audio might include songs you ripped from CDs you own, purchases from Bandcamp and directly from musicians, songs and audio you’ve recorded yourself, and DRM-free iTunes Store items.
However, Apple Music and iTunes Match will replace any song that matches against a song found in the iTunes Store with a 256Kbps AAC file. That may not be desirable, and the matches aren’t always perfect. Apple improved on matching quite a bit a few years ago, but if you have any personal or non-label music, read up on Macworld and other sites about problems you might still encounter before proceeding. If you’ve only purchased iTunes Store music, it’s an easy choice.
Dropbox Smart Sync
If you’re a Dropbox user and have multiple Macs or are sharing folders from other people, you might have many gigabytes of files on a laptop that don’t need to be there. The service’s Smart Sync feature, added to all its paid plans in May 2019, lets you choose which files are stored locally and which are available via the Dropbox cloud. Right-click any file or folder in your Dropbox folder, choose the Smart Sync item, and choose Online Only. Unlike iCloud Drive, Dropbox immediately removes synced files, freeing up space. But like iCloud Drive, those files remain in the Dropbox folder, and will be downloaded automatically when you open them.
None of these strategies except Dropbox Smart Sync deletes files locally except when storage space becomes full and there’s no way to force deletion without removing the actual items. If you have plenty of storage left on the Mac you’re migrating from, you might try the bizarre trick of making a large empty file and then duplicating it to start filling storage. macOS will notice storage getting cramped and start removing local, synced files that are stored in iCloud in one of the above forms.
To create this file, launch Applications > Utilities > Terminal, and then type or copy exactly the following and press return:
mkfile 1g ~/Desktop/BigFile.txt
This makes a 1GB file that you can duplicate until macOS feels the pressure. You can check whether material was removed for iCloud storage in several ways:
- In the Finder, make sure View > Show Status Bar, which will show the currently available storage at the bottom of any window showing a folder within the startup drive.
- Select the startup drive in the Finder and choose File > Get Info. macOS shows in the Used section how much is occupied as files are deleted.
- Choose > About This Mac and then click the Storage button and click Manage. This few shows a number of suggestions for deleting files and applications altogether, but can also track how much The Recommendations assistant appears in System Information, offering a variety of ideas about reducing storage.
When consumed storage on your current Mac drops significantly below the size limited of your new drive, you can delete those large files and empty the trash, and then proceed on your migration.