Whatsapp web and Google Authenticator spring to mind. They both use QR codes to associate a mobile device with a web app. Definitely nicer than typing in a long

Whatsapp web and Google Authenticator spring to mind. They both use QR codes to associate a mobile device with a web app. Definitely nicer than typing in a long token, and avoids an extra step of (e.g.) emailing it to you. I never understood the point of using them to share links, it's almost always faster to just type in the URL or Google it (unless, I suppose, you wanted to share a very long or unique URL)