A 256 GB MacBook is a fine development machine until it is not. macOS takes 20 to 30 GB, Xcode takes another 12 to 15 GB, and a few months of normal work leaves you with the “Your disk is almost full” dialog at the worst moment. Here is where the space goes and what you can do about it, in order of how much you get back.

Where it goes

On a 256 GB Mac used for development, these are the usual suspects, largest first.

  • Simulator runtimes. Each iOS, watchOS or visionOS runtime is 7 to 8 GB. Xcode installs a new one with every update and keeps the old ones. Three unused runtimes are 22 GB.
  • DerivedData. Xcode’s build folder. 10 to 25 GB on a machine with a few active projects, and it grows until you delete it. Xcode rebuilds it on its own.
  • Docker’s disk image. One file, usually 20 to 60 GB, holding every image and container you ever pulled. Docker only shrinks it when you ask.
  • node_modules. A few hundred megabytes per project, times every project you cloned this year. 20 to 40 GB is normal.
  • Package caches. npm, pip, Gradle, Cargo, CocoaPods, Homebrew. 5 to 15 GB together, all rebuilt on demand.
  • Old toolchain versions. Node versions in nvm, Python versions in pyenv, JDKs, Rust toolchains. 3 to 8 GB, and you usually need one of them.

What to delete, in order

  1. Simulator runtimes for versions you no longer test. Xcode › Settings › Components, or let Cache Goblin list them with their sizes. They download again if you need them.
  2. DerivedData and package caches. Safe to delete outright. Your next build is slower once and then normal.
  3. node_modules in projects you have not opened in months. npm install brings them back. Keep the ones for projects you touched this month.
  4. Docker images you no longer use. docker system prune removes stopped containers and dangling images. Cache Goblin runs the same command for you and shows what it will reclaim first.
  5. Old toolchain versions, one at a time, after checking which projects pin them.

Together these are typically 40 to 80 GB on a 256 GB Mac, which is the difference between a full disk and a comfortable one.

Keeping it from filling up again

Caches grow back. That is what they are for. The trick is to clear the safe ones on a schedule and to look at the rest a few times a year. Cache Goblin can clean the Safe class automatically on the cadence you choose, and it shows the Restorable and Risky classes in the menu bar so you see the number before the dialog does.

When 256 GB really is too small

If you run a scan and the caches come to 15 GB, the drive is full of your own files and no cleaner will fix that. Move media to an external drive or plan for a bigger configuration on the next Mac. We compared the options and their costs in the cheapest way to add storage to a Mac.

Download Cache Goblin free and run a scan. It takes under a minute and shows exactly which of the items above are on your Mac and how big they are.