For reasons of cost, we might buy a new Mac with a smaller drive than the one we’re replacing. If your current Mac has more data stored than the capacity of the new one, you probably feel you’re in a pickle. But you can strategize how to make this transition work.
When planning the transistion, I highly recommend that you try to keep free at least 50GB on a 256GB drive, and 100GB on drives that are 512GB and larger.
Here’s how you can reduce your storage requirements before migration.
Enable iCloud Photos and set Photos (in Photos > Preferences > iCloud) to store only optimized versions of your images. This does result in you not having the ability to create a full local backup of all your media, and may require an upgrade from your current iCloud storage level. However, it can be worth the tradeoff of hundreds to several hundreds of dollars for a larger-capacity drive on the new Mac.