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.

Xcode “Unable to Boot the Simulator”: Fix

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

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
```
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 <device-udid>   # or: xcrun simctl erase all
```
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
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
```
04
Starting it from Flutter’s side
“Start the simulator (renamed to Device Hub on Xcode 27)” Flutter, Set up iOS development
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; Flutter: Set up iOS development.

Rather hand it over?

Fixed scope, fixed price, paid upfront. The work happens in writing; no call needed.

iOS Simulator errorXcode: “Unable to boot the Simulator” (Flutter, React Native, Xcode)

Why the simulator won’t boot, and the fix

Stale simulator caches after a macOS or Xcode update

The device itself is in a bad state

The iOS simulator runtime is missing or damaged

Starting it from Flutter’s side

Rather hand it over?

More on this error

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