What kind of calls on Telegram have end-to-end encryption?

Telegram’s voice and video calls have end-to-end encryption. This means the call audio and video are encrypted so that only the participants’ devices are intended to access the conversation.

Telegram introduced one-to-one voice calls in 2017 and added one-to-one video calls in August 2020. The calls use a key negotiated between the participants, with Diffie–Hellman key exchange helping establish that session key. Participants can compare visual indicators in the app to help detect a man-in-the-middle attack.

This protection should not be confused with ordinary cloud chats, which use client-server and server-client encryption rather than end-to-end encryption by default. Secret Chats are also end-to-end encrypted, but they are separate, device-specific conversations rather than standard cloud chats.