How to move Google Authenticator to your new iPhone

If you're upgrading to a new iPhone from an old one, or from an Android device, then you need to take steps to make sure that Google Authenticator continues to work as you'd expect.
Google Authenticator on iOSGoogle Authenticator on iOS
Google Authenticator is an app and a service that provides the security benefits of two-step authentication without the risks involved in text messages. If you rely on it, then you tend to use it every day and possibly even multiple times a day, in which case you need it to work with your new device.