Have you ever seen an one time password link in a regular <a> tag?
Here is an example TOTP link from Google Authenticator repo:
The most familiar form for them is QR codes:
Which is a problem if you're alterady on your mobile device and you can't scan it. For this case there is usually a text like "Please manually add the key
JBSW Y3DP EHPK 3PXP to your Authenticator app". But what about the link itself? Well, just try it on your phone: click me.
I'm really shocked that it works perfectly and that I have never seen this simple and very web style solution in action.