In: Software, Privacy.
Also: e-mail.
Backlinks: E-mail, Nostr.

Chat

Less known chat messaging, alternatives to the super popular, spyware infested WhatsApp, Telegram and Signal apps.

Apps

Sorted in semi-alphabetic order.

Bitchat Decentralized Messaging

"Revolutionary" offline messaging app by Jack Dorsey that works without internet using Bluetooth mesh networks.
"Military-Grade Encryption" X25519 key exchange + AES-256-GCM for private messages, Argon2id + AES-256-GCM for channels, Ed25519 signatures.
Always be wary of apps that promise to be "revolutionary" and that they have "military-grade encryption". Bitchat may be indeed secure, but it's not revolutionary; see FireChat, Briar project, Bridgefy, Berty tech, etc.
https://bitchats.app
https://github.com/permissionlesstech/bitchat

Briar

Censorship-resistant peer-to-peer messaging that bypasses centralized servers.
Connect via Bluetooth, Wi-Fi or Tor, with privacy built-in.
From what I understand, Briar is leaking lots of metadata about your conversation.

Bridgefy

Bridgefy is a free messaging app that works without the Internet. In case of natural disasters, large events, or at school.
iOS and Android apps.

https://bridgefy.me
https://bridgefy.me/blog
https://github.com/bridgefy -- source code

Cwtch

Cwtch (/kʊtʃ/ - a Welsh word roughly translating to "a hug that creates a safe place") is a decentralized, privacy-preserving, multi-party messaging protocol that can be used to build metadata resistant applications.
Apps for Windows, Mac, Linux and Android.

https://docs.cwtch.im
https://fosstodon.org/@cwtch
https://git.openprivacy.ca/cwtch.im -- source code

FireChat

FireChat was a proprietary mobile app, developed by Open Garden, which used wireless mesh networking to enable smartphones to pass messages to each other peer-to-peer via Bluetooth, Wi-Fi, or Apple's Multipeer, without an internet connection.

Jami

Jami is a free/libre, end-to-end encrypted, and private communication software.

https://jami.net
https://mstdn.io/@Jami
https://git.jami.net/explore -- source code

Intercom

iNtercom acts like a simple walkie talkie (two way radio).

Session

Session is an end-to-end encrypted messenger that protects your personal data. Take back control with a messaging app designed, built, and operated by a global community of privacy experts.
iOS, Android, Mac, Linux, Windows apps.

https://getsession.org
https://mastodon.social/@session
https://github.com/session-foundation -- source code

SimpleX

SimpleX - the first messaging network operating without user identifiers of any kind - 100% private by design!
iOS, Android, Mac, Linux, Windows apps.

https://simplex.chat
https://lemmy.ml/c/simplex
https://github.com/simplex-chat/simplex-chat
https://github.com/simplex-chat/simplex-chat/blob/stable/docs/CLI.md -- terminal CLI for Linux/MacOS/Windows

Tox

Probably not super safe, but worth mentioning.

https://tox.chat
https://tox.chat/clients.html -- Tox Clients
https://en.wikipedia.org/wiki/Tox_(protocol)
https://github.com/TokTok/c-toxcore -- source code

Wire

Enterprise-grade messaging, calls, and file sharing protected by invisible, always-on MLS encryption and compliant with the world's strictest standards.
I don't recommend it.

https://wire.com
https://github.com/wireapp/wire -- source code

Protocols

We have IRC, XMPP, Jami, Nostr, Secure Scuttlebutt (SSB) and Matrix.
XMPP is generally preferred, because it can be easily hosted.
Nostr has tons of apps, probably 0xchat.com is the closest to chat (NIP-04 DM, Gift-Wrapped DM, Secret DM).
Matrix is just unstable and generally crappy.
IRC is centralized and not secure by default.