Zulip vs Slack

Zulip and Slack both land on Depends.

Zulip

Depends

Confidence: Medium

Buy if your distributed team or community drowns in chat noise and will commit to the topic-threading model.

Depends

Confidence: Low

Confidence is low: only Slack's own marketing/security page was available for review.

Zulip versus Slack
Compare	Zulip	Slack
Verdict	Depends	Depends
Best for	Distributed teams drowning in chat noise	Distributed teams coordinating in channels
Who it's not for	Teams wanting a drop-in Slack replacement with zero onboarding	Solo founders or 1-3 person teams . platform weight is overkill
Privacy	Active security program (HackerOne disclosure, prompt releases), but multiple CVEs landed in 2025-26 including an authentication bypass.^³	No known public vulnerabilities found in the sources reviewed.¹³
Support quality	No direct support-quality evidence found	No support evidence in sources reviewed
Public sentiment	Reviewers consistently praise Zulip's organized, threaded conversations and pricing while admitting an adjustment period versus Slack.^⁵	No independent user reviews were found in the sources reviewed.
Biggest gotcha	Self-hosters own updates: 2025-26 brought auth-bypass and info-disclosure CVEs^³	Guess: Enterprise Key Management is likely a paid add-on . confirm before budgeting.¹³