# Xcode: “Unable to boot the Simulator” (Flutter, React Native, Xcode) > Unable to boot the Simulator from Xcode, Flutter or React Native. Clear the simulator caches, erase the device, or reinstall the iOS simulator runtime. Canonical: https://app369.com/fix/xcode-unable-to-boot-the-simulator/ Last updated: 2026-11-08 flutter run, npx expo run:ios or Xcode stops with Unable to boot the Simulator, often right after a macOS or Xcode update. The simulator service can’t start the device: its caches are stale, the device’s data is in a bad state, or the iOS simulator runtime it needs is missing or damaged. **Short answer** Quit Simulator and Xcode. Delete the simulator caches (rm -rf ~/Library/Developer/CoreSimulator/Caches) and restart the Mac. If it still fails, erase the device with xcrun simctl erase, or reinstall the iOS runtime from Xcode, Settings, Components (or xcodebuild -downloadPlatform iOS). ## **Why the simulator won’t boot, and the fix** 1. 01 ### **Stale simulator caches after a macOS or Xcode update** The most common fix. Quit Simulator and Xcode, delete the caches folder, then restart the Mac so the simulator service starts fresh. Apple doesn’t document this folder; it rebuilds on its own, and the next boot is slower.``` rm -rf ~/Library/Developer/CoreSimulator/Caches # then restart the Mac ``` 2. 02 ### **The device itself is in a bad state** One device that won’t boot while others do usually has damaged data. Shut everything down and erase it. Erasing wipes the apps and data on that simulator only.``` xcrun simctl shutdown all xcrun simctl list devices xcrun simctl erase # or: xcrun simctl erase all ``` 3. 03 ### **The iOS simulator runtime is missing or damaged** > “To download iOS platform support and the latest iOS Simulator runtimes, run the following command in your preferred terminal.” [**Flutter, Set up iOS development**](https://docs.flutter.dev/platform-integration/ios/setup) After an Xcode update the runtime for your device’s iOS version may be gone or half installed. Open the Components settings, remove a broken runtime and get it again, or download it from the terminal.``` xcodebuild -downloadPlatform iOS ``` 4. 04 ### **Starting it from Flutter’s side** > “Start the simulator (renamed to Device Hub on Xcode 27)” [**Flutter, Set up iOS development**](https://docs.flutter.dev/platform-integration/ios/setup) Once the runtime is installed, open the simulator first and let Flutter find it, instead of launching a device that no longer exists.``` open -a DeviceHub # Xcode 27 open -a Simulator # Xcode 26 or earlier flutter devices flutter run ``` Checked against the vendor’s docs on November 8, 2026: [Apple: Downloading and installing additional Xcode components](https://developer.apple.com/documentation/xcode/downloading-and-installing-additional-xcode-components); [Flutter: Set up iOS development](https://docs.flutter.dev/platform-integration/ios/setup). ## **Rather hand it over?** Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed. - [from $450**App Fix Ticket**One reproducible bug in an existing mobile or web app, diagnosed and fixed.**See scope and start**](https://app369.com/fixed-price/flutter-firebase-bug-fix/) - [from $450**AI-Built App Rescue**A Lovable, Bolt or Cursor app checked end to end in 3 days, then its worst problems fixed at a fixed price.****No issues worth fixing, no charge.**** If the Launch Check finds nothing rated medium or higher, Simon refunds the full $450. You keep the report either way. This applies to the first 10 Launch Checks bought after October 30, 2026.**See scope and start**](https://app369.com/fixed-price/ai-app-rescue/) Related: [**Xcode PhaseScriptExecution failed**](https://app369.com/fix/xcode-phasescriptexecution-failed/) · [**Flutter pod install failed**](https://app369.com/fix/flutter-pod-install-failed/) · [**Xcode “Signing requires a development team”**](https://app369.com/fix/xcode-signing-requires-development-team/) · [**Xcode provisioning profile invalid or expired**](https://app369.com/fix/xcode-provisioning-profile-invalid-or-expired/) Questions ## **More on this error**
**My Mac is low on disk space. Can that cause it? **+ Yes. Each simulator runtime and device takes several gigabytes, and a full disk stops devices from booting. Remove runtimes you no longer use in Xcode, Settings, Components, and delete unavailable devices with xcrun simctl delete unavailable.
**Where did the Simulator app go in Xcode 27? **+ Flutter’s setup guide says the simulator is renamed to Device Hub on Xcode 27. Open it with open -a DeviceHub; on Xcode 26 or earlier, open -a Simulator.
**Can you fix it for me? **+ If one bug is the whole problem, the App Fix Ticket covers it: a written diagnosis first, then the fix. If the app has more going on, the Launch Check is a written check of the whole app. Each issue found is rated critical, high, medium or low, with where it is and how it was confirmed. No issues worth fixing, no charge. If the Launch Check finds nothing rated medium or higher, Simon refunds the full $450. You keep the report either way. This applies to the first 10 Launch Checks bought after October 30, 2026.
A different error? ## **Describe it and get a written quote** Send the error and what you were doing. You get a written scope, a fixed price and a timeline; Simon replies by email, usually within one business day. [**Describe your problem **→](https://app369.com/contact/) [**All fixes**](https://app369.com/fix/)