Zulip

Zulip provides an organized team chat environment that separates discussions into topic‑based threads, allowing users to follow multiple conversations without losing context. Its design supports both live and asynchronous messaging, making it suitable for remote and flexible work across distributed teams of any size. The application is available as a self‑hosted service on Ubuntu, Debian, or Docker, and also as a cloud offering with a free tier for qualifying organizations.

The software is open source under the Apache‑2.0 license, with a large and active contributor community that maintains extensive documentation, testing, and code readability. It includes desktop and mobile clients, integrations, and an API, and it is used by Fortune 500 companies, open‑source projects, educational institutions, and research groups. Its focus on structured threading helps teams manage knowledge, make decisions faster, and keep conversations searchable over time.