Twitter is giving non-Blue subscribers 30 days to subscribe to its paid service or have their text message two-factor (2FA) authentication disabled. In a blog post on Wednesday, the company announced text-based 2FA would be a Blue feature, but the other options, which involve using an authenticator app or a security key, will still be free.

“While historically a popular form of 2FA, unfortunately we have seen phone-number based 2FA be used – and abused – by bad actors,” the company wrote. While 2FA with SMS has now been made a paid feature, the company said its availability may vary by country and carrier.

“After 20 March 2023, we will no longer permit non-Twitter Blue subscribers to use text messages as a 2FA method. At that time, accounts with text message 2FA still enabled will have it disabled. Disabling text message 2FA does not automatically disassociate your phone number from your Twitter account.”

“We encourage non-Twitter Blue subscribers to consider using an authentication app or security key method instead. These methods require you to have physical possession of the authentication method and are a great way to ensure your account is secure,” the company shared.

Twitter Blue is available on Android, iOS and the web with a monthly between $8 to $11 or a discounted $84 annual fee.