{"data":{"slug":"zulip","name":"Zulip","tagline":"Apache-2.0 team chat organised by topic threads; self-host or use Zulip Cloud","category":"comms","categoryName":"Comms","url":"https://zulip.com","github":"https://github.com/zulip/zulip","pricing":"open-source","hook":"Zulip is open-source team chat where every message belongs to a channel and a topic, so conversations stay threaded and you can catch up topic by topic instead of scrolling one stream.","whatsGood":"Apache-2.0 (zulip/zulip), server release 12.3 (2026-09-21), commit on 2026-10-21. ★~26k (~45 a week), developed since 2015. Useful for remote or open-source teams that want a Slack alternative they can self-host, with a REST API, bots and webhook integrations.","theCatch":"The self-hosted server is a substantial install (Postgres, RabbitMQ, Redis, memcached, nginx) and wants its own VM. Mobile push notifications from a self-hosted server go through Zulip's push service, which is only free up to a certain size. The topic model takes a week or two to get used to.","verdict":"The best open-source Slack alternative if your team likes threads.","addedAt":"2026-10-21","featured":false,"domain":"Comms","subSpecialty":"Realtime","subcategory":"Team Chat","tags":["self-host","permissive","active"],"capabilities":[],"surfaces":["Self-host"],"ecosystem":["Multi-platform"],"licenseModel":"Apache-2.0","githubStars":26085,"starsPerWeek":45,"access":"free","archived":false,"repo":{"createdAt":"2015-09-25","pushedAt":"2026-10-21","license":"Apache-2.0","archived":false,"checkedAt":"2026-10-21"}},"related":[{"slug":"livekit","name":"LiveKit","tagline":"Apache-2.0 realtime rooms, SFU, and agents"},{"slug":"chatwoot","name":"Chatwoot","tagline":"MIT-core support inbox you can self-host for $0/agent"},{"slug":"socket-io","name":"Socket.IO","tagline":"MIT realtime library with fallbacks, not a hosted product"},{"slug":"plunk","name":"Plunk","tagline":"AGPL-3.0 transactional email, workflows, and broadcasts"},{"slug":"centrifugo","name":"Centrifugo","tagline":"Apache-2.0 Go realtime server binary, not in-process Socket.IO"}],"links":{"self":"/api/gems/zulip","html":"/gems/zulip","markdown":"/gems/zulip.md","category":"/api/gems?category=comms","categoryPage":"/stacks/comms"}}