Telegram

Telegram is a messaging app that focuses on “speed and security” and describes itself as “like SMS and email combined”. The product is a cloud-based messenger that allows users to share messages, photos, videos, and files, with conversations synced across all of a user's devices at the same time. Users can also create groups of up to 200K people in size. Telegram also offers privacy features such as device-specific secret chats which are end-to-end encrypted, as well as end-to-end encryption for voice or video calls. Group or private chats not employing the “secret chat” feature are not end-to-end encrypted but instead protected by what Telegram describes as server-client encryption.