checked on github

TotP worked great. good thing, cuz Firefox forced me to use it to write this review :)
It supports multiple keys... just add another and it adds an option. I REALLY like the privacy consciousness of the add-on.

simplest TOTP addon ever. Really great.

So useful! Thanks!

It wont sync across firefox instances, because the extension identifier is unique per installation. You can still manually retrieve the token from the synced firefox password manager though.