Zulip

Zulip takes a different approach to team chat than Slack or Microsoft Teams by organizing conversations around topics within channels — a structure that makes it possible to follow asynchronous conversations without reading everything that happened while you were away. This design was developed at Zulip's original parent company, acquired by Dropbox in 2014 before the founding team left and open-sourced the product under Kandra Labs. The topic-threading model resonates particularly with communities doing technical work — software development teams, open-source projects, academic research groups — where conversations about discrete problems benefit from being clearly delimited rather than flowing in a linear stream.

Zulip Cloud is the hosted offering from Kandra Labs, while self-hosted deployment on the open-source version is common in the developer and academic communities. Zulip's notification model is designed for asynchronous communication — it tracks which messages are new since your last read position rather than just the most recent N messages — which places particular demands on the read-state synchronization backend. The email integration, which lets users reply to Zulip messages from email, adds an inbound and outbound mail dependency to the platform's infrastructure. The API is extensively documented and widely used, particularly in developer communities that have built bots and integrations on top of it.

When Zulip Cloud is degraded, users encounter message delivery failures where sent messages appear locally but do not arrive for other participants. The web client may lose its WebSocket connection and fall back to polling, which works but delivers new messages with noticeable delay rather than instantly. Mobile push notifications stop arriving during push relay problems, silently breaking the notification chain for users who depend on mobile alerts to know when to respond. The read-state sync that Zulip's threading model depends on can desync during backend problems, causing the unread count to be incorrect until the client reconnects and re-fetches state from the server.

Outage.gg tracks Zulip Cloud service status using community reports from users across web, mobile, and desktop clients. If messages are not delivering, notifications are down, or the service is not connecting, the live status page shows current impact from the Zulip user community.