Changes to login and sign-up for third-party applications

[Lonami]

On the 10th of February, Telegram sent this message to those with an application registered on https://my.telegram.org:

Telegram API Update. Hello ▒▒▒▒,. Thank you for contributing to the open Telegram ecosystem by developing your app, ▒▒▒▒.

Please note that due to recent updates to Telegram's handling of SMS and the integration of new SMS providers like Firebase, we are changing the way login codes are handled in third-party apps based on the Telegram API.

Starting on 18.02.2023, users logging into third-party apps will only be able to receive login codes via Telegram. It will no longer be possible to request an SMS to log into your app – just like when logging into Telegram's own desktop and web clients.

Exactly like with the Telegram Desktop and Web apps, if a user doesn’t have a Telegram account yet, they will need to create one first using an official mobile Telegram app.

We kindly ask you to update your app’s login and signup interfaces to reflect these changes before they go live on 18.02.2023 at 13:00 UTC.

This change will not significantly affect users since, according to our research, the vast majority of third-party app users also use official Telegram apps. In the coming months, we expect to offer new tools for third-party developers that will help streamline the login process.

What this means for Telethon:

• You can no longer use Telethon to sign up.
• You will only be able to receive the code via Telegram. Not SMS.

Why has Telegram done this? Probably in an attempt to reduce spam, and also because sending SMS is likely not cheap at their scale. Another possible reason may be security. We cannot know. Telethon cannot do anything to bypass these new limitations, and won't try playing tricks to do so.

[Lonami]

For additional context, see #3835 and other linked issues.

Discussion happened in https://t.me/TelethonChat/529422, and this was also posted in https://t.me/TelethonUpdates/1329.