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How do you delete old iOS simulator runtimes on a Mac?

/System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime
/Library/Developer/CoreSimulator/Cryptex
/Library/Developer/CoreSimulator/Caches/dyld

By Parsa Nasirimehr

Remove runtimes in Xcode › Settings › Components, or with xcrun simctl runtime delete, not by deleting files: they sit in protected system folders, one runtime can span two folders, and macOS keeps track of them. Check the folders afterwards, because simctl's total doesn't always match what's on disk.

How big it gets

On the Mac we measured, a working developer's Mac on macOS 27: 37.7 GB of runtime images for four runtimes by du, plus 3.8 GB of simulator caches. xcrun simctl runtime list reported 28.6 GB: iOS 18.6 is stored as two images, a 9.1 GB parent in AssetsV2 and an 8.8 GB image in Cryptex, and the total counts only the second. du counts APFS clones twice, so the real difference may be smaller.

What it is

What writes itXcode, when you download a platform in Settings › Components or when a new Xcode adds its own iOS and watchOS runtimes. Each runtime is a disk image of a whole iOS, watchOS, tvOS or visionOS.
Sizes hereiOS 27.0 8.1 GB, iOS 27.1 7.9 GB and watchOS 27.0 3.8 GB, each one image in AssetsV2. iOS 18.6, an older-style runtime, has two: its 9.1 GB parent image in AssetsV2 and an 8.8 GB image in /Library/Developer/CoreSimulator/Cryptex. xcrun simctl runtime list -v shows both paths.
Why it growsXcode updates add runtimes and never remove the old ones. A runtime you tested on once stays until you remove it: iOS 18.6 here was last used on 25 October.
CachesCaches/dyld holds a shared library cache per runtime, 3.8 GB here. The simulator rebuilds it the next time it boots that runtime, which makes that first boot slower.
Counted asSystem Data in Storage settings, because the images live in system folders. Their mounted copies under /Library/Developer/CoreSimulator/Volumes take no extra space; don't add them up with du.

How to clear it

  1. See what you have and when each runtime was last used: xcrun simctl runtime list -v
  2. Remove the ones you no longer test on in Xcode › Settings › Components, or with xcrun simctl runtime delete <id>. xcrun simctl runtime delete --notUsedSinceDays 30 --dry-run shows which runtimes a month unused would go; run it again without --dry-run to delete them.
  3. Then remove the simulators that ran on them: xcrun simctl delete unavailable
  4. Measure /System/Library/AssetsV2/com_apple_MobileAsset_iOSSimulatorRuntime and /Library/Developer/CoreSimulator/Cryptex with du -sh before and after.

What you lose: Testing on that OS version until you download it again from Xcode, which takes 8 to 9 GB and a while. Your projects and other simulators are untouched.

With Scrubs: Scrubs's Quick Wins lists simulator runtimes with their size and a link to Xcode's Components settings, where Apple wants them removed, and its map shows the runtime folders that Storage settings files under System Data. Download Scrubs; scanning is free.

Related folders

CoreSimulatorWhy is CoreSimulator taking up so much space on my Mac?DerivedDataWhat is DerivedData on a Mac, and can you delete it?iOS DeviceSupportWhat is iOS DeviceSupport on a Mac, and is it safe to delete?

Sizes measured with du on 3 November 2026. Paths and commands apply to macOS 15 and later. See also how to free up disk space on a Mac.

About the author: Parsa Nasirimehr is a mobile app developer who builds Scrubs, a disk map for the Mac. Spotted something wrong? Write to support@getscrubs.app.