When you start the Xcode Simulator, you may see the "Unable to boot the Simulator" Error:

This error may occur when the Developer Storage Cache contains corrupted files. You may try to clear the Developer Storage Cache to resolve this issue.

Steps to Clear Developer Storage Cache

1. Open System Settings

2. Search for "Storage" and then select "Storage Settings"

3. Select "Developer" under "Storage Settings" by clicking the icon "i" next to "Storage." The "Developer" storage window pops up.

4. Select Xcode Caches, Project Archives, Project Build Data and Indexes one at a time and click the "Delete..." button to delete them.

5. Now you can try to open the Xcode Simulator App and the "Unable to boot the Simulator" error may be resolved.