Why can't I use SMS two-factor authentication on Twitter? How can I increase security on Twitter without SMS?
Twitter requires a paid subscription for Twitter Blue to use SMS two-factor authentication. While SMS or text messaging is a popular way to increase security, the new company policy is to reduce abuse by "bad actors" by demanding Twitter Blue membership for the service. This does not mean that 2FA cannot be used by those without a blue check mark on Twitter.
Anyone wishing to utilize 2FA on their Twitter account can use an authentication app for free. This alternative to SMS two-factor authentication syncs a changing code on your iPhone with the Twitter sign in page. Several options can be used, including Google Authenticator.Once an authenticator app is installed on your device, go to Security and account access under Twitter settings. Check the box next to Two-factor authentication -> Authenticator app and follow the prompts to set up 2FA.