head to head · open source
cobalt vs Zulip
cobalt has 45,722 GitHub stars, 4,031 forks, 269 open issues and last shipped 7 months ago. Zulip has 26,158 stars, 10,521 forks, 2,008 open issues and last shipped yesterday. cobalt leads on adoption by 75% (45,722 vs 26,158 stars). cobalt is written in Svelte under AGPL-3.0; Zulip is written in Python under Apache-2.0. cobalt has attracted 9% as many forks as stars, Zulip 40%. Zulip was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 2 topic tags (collaboration, javascript), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| cobalt | Zulip | |
|---|---|---|
| GitHub stars | ★ 46K | ★ 26K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | Svelte | Python |
| Last push | 2026-04-06 | 2026-11-02 |
| Forks | ⑂ 4.0K | ⑂ 11K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick cobalt if
- You weight community size — 46K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Svelte
- You value the larger contributor base for long-term maintenance
pick Zulip if
- You want the Zulip feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Python
- You evaluated both and Zulip fits your workflow better
About cobalt
best way to save what you love cobalt.tools 💬 community discord server 🐦 twitter 🦋 bluesky cobalt is a media downloader that doesn't piss you off. it's friendly, efficient, and doesn't have ads, trackers, paywalls or other nonsense. paste the link, get the file, move on. that simple, just how it should be. cobalt monorepo this monorepo includes source code for api, frontend, and related packages: api tree & readme web tree & readme packages tree it also includes documentation in the docs tree: how to run a cobalt instance how to protect a cobalt instance cobalt api instance environment variables cobalt api…
read the full cobalt overview →
About Zulip
Zulip overview Zulip is an open source organized team chat app with unique [topic based threading][why zulip] that combines the best of email and chat to make remote work productive and delightful. Fortune 500 companies, [leading open source projects][rust case study], and thousands of other organizations use Zulip every day. Zulip is the only [modern team chat app][features] that is designed for both live and asynchronous conversations. Zulip is built by a distributed community of developers from all around the world, with 99+ people who have each contributed 100+ commits. With over 1,500 contributors merging…
read the full Zulip overview →
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Frequently asked questions
Is cobalt or Zulip more popular?
cobalt has 45,722 GitHub stars and Zulip has 26,158. cobalt has the larger community by that measure.
Are cobalt and Zulip free?
Both are open source. cobalt is licensed under AGPL-3.0 and Zulip under Apache-2.0. Neither carries a licence fee.
What is the difference between cobalt and Zulip?
cobalt is written in Svelte and Zulip in Python. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, cobalt or Zulip?
Choose cobalt if you want the larger community (45,722 stars) or its AGPL-3.0 licence terms. Choose Zulip if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.