在 Twitter 上看到他們自家更新了 2FA 的機制，除了本來的 in-app verification 外，也提供常見的 HOTP 了：(掃 QR code，然後會產生六碼數字的那種)
We’re rolling out an update to login verification.
You’ll now be able to use a third party app for two-factor authentication instead of SMS text messages.https://t.co/UXl3xKLEaG
— Twitter Safety (@TwitterSafety) December 20, 2017
在上面的「How to use login verification」連結可以看到 HOTP 的設定方式：
- [...]
- You will see a pop-up window displaying a QR code. Follow the instructions listed.
- To set up the third-party authenticator app, you will need to scan the QR code. You will then see a 6-digit numeric security code.
- Enter this code in the Security code text field in the pop-up window.
- Click Done.
還是可以選擇本來的方式以及簡訊，現在則是多了個選擇...