Telegram

Telegram is a messaging app launched in 2013 by the brothers Pavel and Nikolai Durov, who had earlier founded VKontakte, a large Russian social network. It works like other chat apps, with text, voice notes, calls, photos and files, and it is used by hundreds of millions of people around the world.

Its big difference is that it is built around the cloud. Ordinary chats are stored on Telegram's servers, encrypted between your device and the server, so you can open them from your phone, your laptop and a browser at the same time, with no backup to manage. The trade-off is that they are not end-to-end encrypted by default: Telegram could technically read them. For that you have to start a secret chat, which is end-to-end encrypted, lives only on the two devices and works one to one. Telegram uses its own encryption protocol, called MTProto, instead of the widely studied Signal protocol.

Telegram is also part social network. Groups can hold up to 200,000 members, and channels let one account broadcast to an unlimited audience, which made it popular with news outlets, communities and also with scammers and criminal groups. Anyone can build a bot on it through an open API. It is free, and makes money from a premium subscription and ads in large public channels.