Tox

It provides a peer‑to‑peer instant messenger that operates without central servers, using libsodium‑based encryption for all communications. The core library supports text messaging, encrypted voice and video calls, screen sharing, file transfer, and group chats. Clients can be built from the open‑source code, which is released under GPL‑3.0 and can be self‑hosted or run without a subscription.

The software is aimed at users who prioritize privacy and want a free, advertising‑free alternative to mainstream services. Because the network is distributed, there is no single point of failure or authority that can be compelled to hand over data. The implementation includes callbacks for handling events such as friend requests and messages, and it can compile optional audio/video support when libvpx and Opus are present.

Distinctive aspects include the fully encrypted, serverless architecture and the commitment to openness: the code is libre, the protocol is documented, and the project is maintained by a community rather than a corporation. While the cryptographic model is still experimental and not independently audited, the underlying libsodium library provides proven encryption primitives.