Mac storage cannot be swapped. Apple solders the flash to the logic board and prices each size step at $200 to $400 on the configurator, checked 15 September 2026, and you can only buy it with a new Mac. When the disk fills up you are choosing between an external drive, a new machine, or clearing the one you have. With flash prices two to three times what they were in late 2025, the order of those options matters more than it did.
Option 1: free the space you already paid for
Cost: nothing for a scan, a one-time license if you want the app to clean for you.
Developer tools keep caches that nobody empties. On a Mac used for development for a year or two, they add up to 60 to 90 GB. Xcode’s DerivedData and unused simulator runtimes, Docker’s disk image, node_modules in projects you stopped touching, old Ollama models, Gradle and Cargo caches. Some of this the tools rebuild by themselves after you delete it, and some comes back with a download.
This is the option to try first because it is free to check. Run a scan, look at the Safe total and the Restorable list, and you know within a minute whether the drive is actually full. We wrote up what typical setups find.
When it is enough: your disk is 30 to 100 GB short of comfortable, and you develop software on it.
When it is not: you edit video, keep a photo library on the internal drive, or the scan comes back with a small number.
Option 2: an external SSD
Cost: about $90 for 1 TB at current prices, more for a Thunderbolt enclosure.
A good USB4 or Thunderbolt drive is fast enough to keep project folders and even Docker’s data on. It is also a cable and a thing to carry. Some caches can be moved to it, such as DerivedData with an Xcode setting, and many cannot without symlinks that break in confusing ways.
When it is enough: you have large media, VM images or datasets that do not need to be on the internal drive.
When it is not: the things filling the disk are caches and build outputs, which want to be fast and local. Then you are paying for a drive to hold files that a scan would have deleted.
Option 3: a bigger Mac
Cost: the price of a new machine, plus $200 to $400 per storage step at checkout.
Built-in storage is the most expensive way to buy flash, and it is the only way to get more of it inside a Mac. That makes the comparison simple: a scan that costs nothing, a $29 license if it finds enough, or the next machine. If the machine is due for replacement anyway, buy the storage you will need in three years. If it is not, do the cheaper two options first.
The order that saves the most
- Scan the disk and clean what is safe. Free.
- Move media and archives to an external drive if you have them. Cheap.
- Buy the bigger configuration when you buy the next Mac, sized by what the first two steps told you. Expensive, but once.
Download Cache Goblin free to run the scan. It shows every cache with its size and does not delete anything until you tell it to.