Blog / Sep 20, 2026 · 3 min read
iOS Simulators and CoreSimulator Are Quietly Eating Your SSD
If you’ve ever booted the iOS Simulator, you’ve got a CoreSimulator folder on your Mac that grows every time Xcode ships a new runtime — and it never cleans itself. Each simulator device you’ve created holds a full writable system image, and each iOS runtime is a multi-GB download. Together they routinely add 20–60 GB that looks like your app until you realize it’s just simulators.
Here’s how to see them, delete the ones you don’t use, and keep the ones you do.
Where the gigabytes live
Everything simulator-related hangs out under:
~/Library/Developer/CoreSimulator/Devices
~/Library/Developer/CoreSimulator/Images
~/Library/Developer/CoreSimulator/Volumes
~/Library/Developer/Xcode/iOS DeviceSupport
Measure the damage first:
du -sh ~/Library/Developer/CoreSimulator/*
Devices is the whale: each simulator device’s data + caches. Images + the runtimes downloaded under ~/Library/Developer/CoreSimulator/Runtimes are the multi-GB framework downloads.
Safe to delete? Here’s the map
| Path | What it is | Safe to delete? |
|---|---|---|
CoreSimulator/Devices/*.data | Simulator device data (your apps’ sandboxes inside sim) | Deleting a device is fine — apps you ran on it are reinstallable |
CoreSimulator/Images | Downloaded runtime images | Yes — Xcode re-downloads |
CoreSimulator/Volumes | Mounted runtime caches | Yes (runtime re-mounts) |
Xcode/iOS DeviceSupport | Device symbol/debug files | Yes — regenerated when you plug the device back in |
DerivedData | Build artifacts | Yes — see our DerivedData guide |
The clean way (not manual rm)
1. Close the Simulator first
Quit the Simulator app so the devices aren’t in use. Otherwise Xcode re-creates the device on the next launch and you’re back to square one.
2. Delete simulators you don’t use
Open the Simulator → File → Device → iOS Simulators (or Xcode → Window → Devices and Simulators → left panel). Select old ones → Delete. Each deletion reclaims its entire .data directory — no CLI needed.
The terminal version for a specific device ID:
xcrun simctl delete
# list all first:
xcrun simctl list devices
⚠️ One iron rule:
simctl delete allis permanent. Only delete the devices on your list, never the runtimes your active projects still target.
3. Delete unused runtime downloads (the multi-GB part)
The runtimes themselves (Runtimes folder) are separate from devices — you can keep your current iOS version and drop older ones:
xcrun simctl runtime list
xcrun simctl runtime delete
Or the click path: Xcode → Settings → Components tab → click the minus on runtimes you no longer target. This is the fastest multi-GB win for Xcode money, because old runtimes are just dead downloads your current projects don’t compile for.
4. Nuke the stale caches
With the Simulator quit:
rm -rf ~/Library/Developer/CoreSimulator/Caches
rm -rf ~/Library/Developer/CoreSimulator/Volumes
Xcode rebuilds these on demand. Safe to delete: yes.
The Xcode attic, same theme
Simulators share shelf-space with two other xcode-sized families:
~/Library/Developer/Xcode/DerivedData— 20–60 GB of build artifacts, cleared with our DerivedData guide~/Library/Developer/Xcode/Archives— every archived build you’ve shipped, multi-GB each~/Library/Developer/Xcode/iOS DeviceSupport— duplicate symbol files across device IDs
Our full developer cleanup playbook (free-up-disk-space) covers clearing these in the right order.
See it before you delete it
Simulator bloat is perfect to eyeball: sort by size and the old runtime downloads become obvious. DiskInsight shows every folder’s true byte count (CoreSimulator, DerivedData, running Docker.raw, everything), so you pick which gigabytes go — staged to the Trash, reversible, never auto-deleted. 100% local, no telemetry.
Bottom line
iOS simulators are the quietest disk hog on a dev Mac: devices + runtimes that grow on their own and never shrink. Delete unused devices via Simulator, old runtimes via Xcode Components (or simctl runtime delete), and strip the caches — you keep your active toolchain and lose 20–60 GB of dead weight.
Get DiskInsight Pro · $9.99 one-time like me — find simulators, DerivedData, and the rest of the dev-cache family in one scan.