How to Fix “SimulatorShutdownUnexpectedlyError: Simulator was shutdown during an update” in Xcode

“SimulatorShutdownUnexpectedlyError: Simulator was shutdown during an update” means the Simulator process used by a SwiftUI preview exited while Xcode was refreshing the canvas. First determine whether the failure is limited to previews or affects the Simulator and normal app launches as well.

Example
Common conditions
Recommended fix
Alternatives
Last resort: erase one Simulator
How to verify the fix
Important notes
Summary
References

Example

PREVIEW UPDATE ERROR
SimulatorShutdownUnexpectedlyError:
Simulator was shutdown during an update

This message is not necessarily a Swift compilation error. A transient preview failure, an unavailable runtime, memory pressure, or a crash during preview initialization can all terminate the Simulator process.

Common conditions

The app builds normally but the SwiftUI preview fails.
Xcode or an iOS Simulator runtime was recently updated.
Several Simulators or previews have remained open for a long session.
The preview initializes external SDKs, persistent storage, or network services.
The selected runtime is being downloaded, updated, removed, or is damaged.
The Mac has insufficient memory or free disk space.

Recommended fix

1. Compare the preview with a normal run

Stop and restart the canvas.
Select the same Simulator and choose Product > Run.
If the normal run also fails, investigate the Simulator or app launch rather than the preview canvas alone.

If the app runs but the preview fails, open canvas diagnostics and inspect the preview-process crash or the error immediately before the shutdown.

2. Restart the Simulator service safely

Quit Xcode and Simulator, then shut down running Simulator devices:

xcrun simctl shutdown all

Restart Xcode, boot the destination once in Simulator, and reopen the preview. Restarting the Mac is also a reasonable way to clear a temporary CoreSimulator service problem.

3. Try another Simulator or runtime

Select another device model or installed iOS runtime. If only one runtime fails, inspect it under Xcode Settings > Components or Platforms, depending on the Xcode version. Allow any active download or update to finish.

Removing and reinstalling a runtime takes significant time and disk space. Try another Simulator, restart the Mac, and check free space before reinstalling it.

4. Keep preview initialization lightweight

Inject preview data instead of starting production services:

#Preview {
    ContentView(
        service: PreviewService()
    )
}

Also check for forced unwraps, missing files, persistent-store configuration, and required environment values that may crash only inside the preview process.

5. Refresh build products

Choose Product > Clean Build Folder.
For Swift packages, choose File > Packages > Resolve Package Versions.
Remove this project’s Derived Data only if the problem remains.

If removing Derived Data does not help, stop repeating cache deletion and inspect the runtime and crash diagnostics.

Alternatives

Run the UI normally on the same Simulator while the preview is unavailable.
Split a dependency-heavy screen into smaller views with isolated previews.
If only one Xcode version fails, temporarily use a verified version and retest with the latest stable release.
Submit a reproducible project and preview diagnostics through Feedback Assistant.

Last resort: erase one Simulator

If a single simulated device is damaged, use Device > Erase All Content and Settings in Simulator or erase its specific UDID:

xcrun simctl list devices
xcrun simctl erase <DEVICE-UDID>

Erasing removes the apps and data stored in that Simulator. Target one device instead of erasing every Simulator as a first step.

How to verify the fix

The selected Simulator boots on its own.
The app runs normally on the same destination.
Repeated preview refreshes no longer stop the Simulator.
No new crash appears in preview diagnostics or Console.

Important notes

As of September 16, 2026, Apple has not identified one universal fixed release for every occurrence of this message. Separate preview-only failures, runtime-specific failures, and application initialization crashes before assuming an Xcode defect.

Summary

The error indicates that the Simulator stopped during a preview refresh. Compare with a normal run, restart the Simulator service, test another runtime, and simplify preview dependencies. Reinstall a runtime or erase a simulated device only after narrowing the problem to that component.