Once youve set up some backup numbers, find the Printable Backup Codes option and click Show Backup Codes. Doing so generates a list of ten eight-digit verification codes that you can use in situations where you dont have access to your phone, or where your phone has no service.

Each of these codes can be used only once. Google suggests printing out the list and keeping it in your wallet. You mightmight!consider saving the list in Dropbox or somewhere else in the cloud, so that you can always get to it even if youre without your phone or access to your Google account. Obviously, if someone then figures out your Google password and also breaks into your separate cloud account, they could then break all the way into your Google account, too. You can generate a list of ten new backup verification codes whenever youd like, but doing so invalidates all of your old ones.

Instead of relying on text messages or phone calls, you can instead install the free app. With the app installed, you can generate verification codes even when you have no active network connection. That is, the app can generate codes even when theres no Wi-Fi or cellular signal available for your phone.

First-time setup of the app is a bit confusing. Ignore the login form, and instead tap the Scan Barcode button at the bottom of the screen. (If its not there, tap the Plus (+) button first.)