Yoath

Yoath is a menu bar app that lets you quickly generate two factor codes from a YubiKey and copy them to your clipboard. When you plug in a YubiKey that supports OATH, the app lists your accounts then you can use the menu to quickly generate and copy 2FA codes. If there are multiple accounts for the same issuer (e.g. an app or website), Yoath will automatically group them in a sub-menu to pick the specific account you want the code for. If you add an account after opening Yoath, theres a button to refetch your accounts in there too.

The app is completely open-source so you can see what is going on under the hood if you like. It only uses the LIST and CALCULATE instructions from the YKOATH protocol.

Yoath is READ-ONLY. If you want to add or manage codes use the official Yubico Authenticator app. There's a handy button to open the official app, if you have it installed.