Instant Messengers
Signal
Signal is a popular private messaging, voice call and video call service. All communication between its users is end-to-end-encrypted by default.
Note: You register with your phone number. That’s why Signal requires you to activate your account via a smartphone app.
Website:
XMPP
XMPP (also known as Jabber) is a widely-used free and open internet messaging standard. It’s very easy to use: just register an XMPP account and install an XMPP app. No phone number required.
Because it’s federated, there are lots of sites you can register on. It doesn’t matter if your friends sign up on a different site, all the sites talk to each other.
If these apps and sites are too complicated, try the much easier Zom and Quicksy alternatives. They’re part of the XMPP network as well.
Sign up:
Zom
Zom is an extremely easy to use and free open source messenger app. You don’t need to register to use it, just think of a username.
It’s compatible with the popular XMPP standard used by many other messenger apps, so if you know someone who uses one of those other apps you can message them with Zom.
Android app:
Element / Matrix
Element (previously Riot.im) is a libre instant messaging client based on the Matrix protocol. It includes text chats, audio/video calls and file transfers.
The Matrix protocol has a federated design and allows bridges to other communication apps. Furthermore, anyone can set up their own Matrix server and use it to collaborate with other people’s Matrix servers.
Matrix (sometimes stylized as [matrix][disputed – discuss]) is an open standard and communication protocol for real-time communication. It aims to make real-time communication work seamlessly between different service providers, in the way that standard Simple Mail Transfer Protocol email currently does for store-and-forward email service, by allowing users with accounts at one communications service provider to communicate with users of a different service provider via online chat, voice over IP, and videotelephony. It therefore serves a similar purpose to protocols like XMPP, but is not based on any existing communication protocol.
Sign up:
Desktop app:
Jami
Jami (formerly “Ring”) is a libre easy-to-use alternative to Skype, with voice call, video call and messaging.
It is open source and designed to respect its users’ privacy, with calls going directly from one user to another without using servers. It gives all its members a unique code, which they can share with others, so that they can add each other on the service.
Website:
Threema is a paid open-source end-to-end encrypted instant messaging application for iOS and Android.[6]
The software is based on the privacy by design principles as it does not require a phone number or any other personally identifiable information.
Briar is an open-source software communication technology, intended to provide secure and resilient peer-to-peer communications with no centralized servers and minimal reliance on external infrastructure. Connections are made through Bluetooth, WiFi, or over the internet via Tor and all private communication is end-to-end encrypted. Relevant content is stored in encrypted form on participating devices. Long term plans for the project include "blogging, crisis mapping and collaborative document editing."
Delta Chat doesn’t have their own servers but uses the most massive and diverse open messaging system ever: the existing e-mail server network. Chat with anyone if you know their e-mail address, no need for them to install DeltaChat! All you need is a standard e-mail account.
Text from delta.chat.
Session is an open-source, public-key-based secure messaging application which uses a set of decentralised storage servers and an onion routing protocol to send end-to-end encrypted messages with minimal exposure of user metadata. It does this while also providing common features of mainstream messaging applications.
Private group chat