Apple has increasingly made it hard to mess with macOS system files. That’s true whether you intentionally want to extend macOS’s functionality or if a malicious party is trying to install and activate a virus. However, many system components and all Apple and third-party apps rely on preferences and other files to store your custom settings, caches for work in progress, and other data. If those files corrupt, macOS may be perfectly fine, but you can’t get anything done in an app or your account.

Once you’ve gone through troubleshooting your Mac within your account that doesn’t seem to improve matters, the next big leap before reinstalling macOS is to set up a fresh macOS user account. From this account, you can test hardware, like your Wi-Fi or ethernet adapter; add printers and scanners; or run third-party software that keeps crashing on launch.

Because a fresh account typically contains nothing that would already be corrupted, you can isolate whether a problem is in your everyday user account or a system-wide issue–maybe even hardware related.

Here’s how to set up a fresh, new user account:

• Open "System Settings..." from the  Apple menu

• Go to "Users & Groups"

• Click the "Add User..." button

• Enter your password if prompted

• Choose whether to create a Standard or Administrator account, give it a name, password, and hint, and click "Create User"

When making the account, what kind should it be?

Create a Standard account if you want to test a problem from the perspective of a user without any extra privileges.

Create an Administrator if that’s your normal account type–that’s typical–and you’re trying to perform an apples-to-apples comparison.

• Choose  Apple menu > Log Out [name]

• At the login screen, select the new account, enter the password, and click the arrow to log in

Now you can check if your problem persists.

When you’ve debugged your problem, you can get rid of the account. You must be logged in using an Administrator account to do this.