Rocket.Chat is one of the largest active open source (permissive MIT source license) nodeJS communications platform communities on GitHub, featuring 600+ global community contributors (across projects) from 30+ countries, 15780+ GitHub stars, 3300 forks, 140+ total releases and 6,200+ issues since inception in 2015.

In a world where communication platforms are almost all totally proprietary, privacy-infringing, and centralized (Skype, Slack, WhatsApp, and so on). Rocket.Chat is a breath of fresh air empowering groups around the world to experience a self-hosted, private, distributed and unrestricted communications platform.

Our server is written in NodeJS (server side JavaScript) and utilizes websocket connections to enable real-time interactive rich communications between a variety of clients – including web, mobile (both iOS and Android), and desktop (Windows, macOS, and Linux). Mobile clients are crafted in Swift, Java and Kotlin, we also have a React Native client.

The server is designed to be scalable from a family server on a Raspberry Pi 3, all the way to a cluster of servers for 10s of thousands of communicating users. Its architecture leverages a "modified Kafka’ish optimized MongoDB oplog tailing (single source of truth append-only log) mechanism" to scale across servers in a tunable yet performant manner.

Rocket.Chat has been designed to be totally extensible. REST and realtime (websocket) APIs are available to control and customize various aspects of the server. Extensions can be added modularly using standard node module mechanism.

Chat bots are a popular means of extending the capabilities of Rocket.Chat. Adapters for popular bot framework, such as Hubot, are available and Rocket.Chat’s community published its own integration bots for code platforms including GitHub and Gitlab. Rocket.Chat supports the chat bot and ML, conversational bots, and voicebot communities - with adapters for new bot framework – including the bBot super-bot-framework.