Xcode needs far more space than the download, and keeps needing it
The installer, the simulators, the caches and the archives. Realistic numbers for setting up and living with Xcode on a small drive.
The App Store shows one number for Xcode and it is the least useful of several. What matters is the space needed to install it, the space it occupies afterwards, and the space it will take over the following year, which are three different figures.
Realistic numbers
| Stage | Space needed | Notes |
|---|---|---|
| Download and expand | Roughly double the final size | Both exist at once during install |
| Xcode itself | Around 20 GB | The application bundle |
| One additional simulator runtime | 5 to 8 GB each | iOS, watchOS and tvOS are separate |
| DerivedData after a few projects | 5 to 30 GB | Grows with every build |
| Device support after a few devices | 1 to 3 GB per iOS version | Kept per device version connected |
| Archives | Hundreds of MB per release | Never regenerable |
Installing on a Mac that is short of space
- Clear space before starting, since a failed install leaves a partial download behind.
- Install Xcode without additional platforms, then add only the simulator runtimes you need.
- Delete simulator runtimes for platforms you do not target, with
xcrun simctl runtime delete. - Keep DerivedData on the internal drive; it is written constantly and an external drive is a poor trade for it.
Living with it afterwards
Three folders grow continuously and two of them are safe to clear whenever you like. DerivedData is the largest and rebuilds itself. Simulator devices and runtimes accumulate per iOS version. Archives and device support is the one to be careful with, because archives contain the symbols that make crash reports from shipped builds readable.
If the drive is genuinely too small
An external SSD works for source, simulators and archives but not for DerivedData, which is written to constantly during a build. On a 256 GB Mac doing iOS work, the honest answer is that Xcode plus two simulator runtimes plus a year of caches will use most of it, and a routine for clearing DerivedData is not optional.
Common questions
How much disk space does Xcode need?
Around 20 GB for the application, plus roughly double that during installation because the download and expanded copy coexist. Each additional simulator runtime is 5 to 8 GB, and caches grow continuously after that.
Why is Xcode using more space than it says?
Because DerivedData, simulator runtimes, device support and archives all live outside the application bundle. On one measured Mac, simulator storage alone was 35 GB across two locations.
Can I install Xcode on an external drive?
The application and simulator runtimes work from one, but DerivedData is written constantly during builds and belongs on the internal drive. Splitting it that way is the usual arrangement on a small Mac.
How do I reduce Xcode's disk usage?
Clear DerivedData regularly, delete simulator runtimes for platforms you do not target with xcrun simctl runtime delete, and remove device support folders for iOS versions you no longer test on.