What Telegram feature lets users sign in to third-party websites?

The Telegram feature that lets users sign in to third-party websites is Telegram Login.

Telegram Login is a social-login system that allows a website or app to authenticate a person through an existing Telegram account. Instead of creating another password, the user approves a Telegram login button or authorization flow, and the site receives permitted account information.

The feature was introduced in February 2018 through a website widget connected to a Telegram bot. In its original model, the site could receive a user’s Telegram name, username, and profile picture, while the phone number was not disclosed by default. Developers had to link the login bot to the website’s domain, helping associate the authorization with the intended service.

Telegram Passport is a different feature and a frequent wrong answer. Passport was designed for identity verification using documents such as passports, identity cards, or driver’s licenses. Telegram Gateway is also different: it is a phone-verification service, not the name of Telegram’s general third-party social-login feature.