How to Fix Xcode Simulator ‘launchd failed to respond’

When launching an iOS Simulator from Xcode, you may see “launchd failed to respond” and find that the Simulator will not boot, your app will not run, or the launch process stalls.

This error usually means that launchd inside the simulated device is not responding correctly. It can be caused by a temporary Simulator failure, inconsistent device state, corrupted Simulator data, runtime issues, or stale data left after an Xcode or runtime update.

Common causes
Typical situations where the error appears
What to check first
Solution 1: Restart Xcode and Simulator
Solution 2: Shut down all Simulator devices
Solution 3: Erase the affected Simulator
Solution 4: Delete unavailable Simulator devices
Solution 5: Create a new Simulator device
Solution 6: Reinstall the Simulator runtime
Solution 7: Restart the Mac
Useful commands
Important notes
Summary

Common causes

launchd or another service inside the Simulator failed to start correctly
A previous Simulator session did not shut down cleanly
The data for one simulated device is corrupted
Old Simulator data remains after an Xcode or runtime update
Unavailable Simulator devices are still registered
The CoreSimulator service on macOS is temporarily unstable

Typical situations where the error appears

You may encounter the following message while Xcode is trying to boot a Simulator:

launchd failed to respond

It can also appear after updating Xcode, restarting macOS, switching to another iOS Simulator runtime, or reopening a Simulator that previously failed to shut down correctly.

What to check first

1. Check the current Simulator state

Use the following command in Terminal to list registered Simulator devices and their current state:

xcrun simctl list devices

Check whether the affected device is shown as Booted, Shutdown, or Unavailable.

2. Try a different Simulator device

In Xcode, select another iPhone Simulator as the run destination and try again. If the app launches normally on another device, the problem is likely limited to the original Simulator data.

3. Check the installed Simulator runtime

Open Xcode Settings and check Components or Platforms, depending on your Xcode version. Make sure the iOS Simulator runtime you want to use is installed and available. An incomplete or incompatible runtime can prevent a simulated device from booting correctly.

Solution 1: Restart Xcode and Simulator

Quit both Xcode and Simulator completely, then reopen Xcode and try running the app again. If launchd or CoreSimulator is only temporarily stuck, a normal restart may be enough.

Do not erase Simulator data immediately. Start with a normal restart, try another device, and then shut down all simulators before moving to destructive troubleshooting steps.

Solution 2: Shut down all Simulator devices

If a simulated device is stuck in an inconsistent state, shut down all Simulator devices with simctl:

xcrun simctl shutdown all

Then reopen Simulator or run the app again from Xcode.

Solution 3: Erase the affected Simulator

If the issue affects only one simulated device, erasing that device can clear corrupted state. You can do this from Xcode’s Devices and Simulators window.

To erase all Simulator devices from Terminal, use:

xcrun simctl shutdown all
xcrun simctl erase all

Warning: erase all removes apps, settings, accounts, and test data stored in Simulator devices. Use it only after confirming that you do not need that data.

Solution 4: Delete unavailable Simulator devices

After changing or removing Simulator runtimes, obsolete devices may remain registered. You can remove devices that no longer have a matching runtime with:

xcrun simctl delete unavailable

This is also a useful cleanup step after Xcode or Simulator runtime changes.

Solution 5: Create a new Simulator device

If the existing device appears corrupted, create a new Simulator from Xcode’s Devices and Simulators window and test the same project there.

If the new Simulator works, the original device data was probably the source of the problem.

Solution 6: Reinstall the Simulator runtime

If the same error occurs across multiple Simulator devices, the installed runtime itself may be damaged or incompatible. Open Xcode Settings, locate the relevant platform or component, and reinstall the required Simulator runtime if necessary.

After updating Xcode, also verify that the Xcode version supports the runtime you are trying to use.

Solution 7: Restart the Mac

If restarting Xcode and Simulator does not help, restart macOS. This resets the CoreSimulator-related processes and can resolve a system-wide Simulator service problem.

Useful commands

These commands are useful for checking and recovering Simulator state:

xcrun simctl list devices
xcrun simctl shutdown all
xcrun simctl delete unavailable

Use the following only when you intentionally want to reset Simulator contents:

xcrun simctl erase all

Important notes

Try a normal restart and shutdown all before using erase all
Determine whether the issue affects one Simulator or every Simulator
After an Xcode update, check that the required Simulator runtime is installed and supported
Avoid manually deleting CoreSimulator folders based on old troubleshooting guides unless you have confirmed that it is necessary for your current Xcode version

Summary

The “launchd failed to respond” error usually indicates that launchd inside the simulated device or the surrounding CoreSimulator environment did not start correctly.

Start with restarting Xcode and Simulator → running xcrun simctl shutdown all → testing another Simulator. If the issue is limited to one device, erase or recreate it. If multiple devices fail, check the installed runtime and restart the Mac.