When you switch to a new phone it can be a pain to add your accounts to Google Authenticator. (You are using two-factor authentication with important accounts, right?). This tool allows you to easily generate QR codes for your accounts as long as you have the secret key, without having to disable and re-enable 2-factor authentication on each account. Just fill in the fields, then point your camera to the screen and boom, your account is added.
Hitting enter or tab will update the QR code, or you can hit the Update button.
Note: For the security conscious, your data never leaves your browser. It is never sent to the server. If you don't trust me, save this file to your desktop, disable your network and then generate the QR code.
Updated Feb 15, 2018