head to head · open source
Bluesky vs CatchUp
Bluesky has 18,295 GitHub stars, 2,837 forks, 2,400 open issues and last shipped yesterday. CatchUp has 2,101 stars, 210 forks, 31 open issues and last shipped 3 days ago. Bluesky leads on adoption by 771% (18,295 vs 2,101 stars). Bluesky is written in TypeScript under MIT; CatchUp is written in Kotlin under Apache-2.0. Bluesky has attracted 16% as many forks as stars, CatchUp 10%. Bluesky was the more recently maintained of the two, and both are self-hostable with no licence fee.
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
| Bluesky | CatchUp | |
|---|---|---|
| GitHub stars | ★ 18K | ★ 2.1K |
| License | MIT | Apache-2.0 |
| Written in | TypeScript | Kotlin |
| Last push | 2026-09-17 | 2026-09-15 |
| Forks | ⑂ 2.8K | ⑂ 210 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Bluesky if
- You weight community size — 18K stars and counting
- You want the MIT license terms
- Your stack matches TypeScript
- You value the larger contributor base for long-term maintenance
pick CatchUp if
- You want the CatchUp feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Kotlin
- You evaluated both and CatchUp fits your workflow better
About Bluesky
Bluesky is the open source social application codebase for the Bluesky Social app. It lives in the AT Protocol ecosystem, also called atproto, and it is written in TypeScript as a React Native application. The project provides client code for Web, iOS, and Android, and it builds on open source atproto packages such as @atproto/api, which live in a separate repository.
read the full Bluesky overview →
About CatchUp
CatchUp is an open source Android app written in Kotlin under the Apache 2.0 license. It sits in the Android community and social networking space and gives a short form view of several services instead of asking users to open many dedicated apps.
read the full CatchUp overview →
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Frequently asked questions
Is Bluesky or CatchUp more popular?
Bluesky has 18,295 GitHub stars and CatchUp has 2,101. Bluesky has the larger community by that measure.
Are Bluesky and CatchUp free?
Both are open source. Bluesky is licensed under MIT and CatchUp under Apache-2.0. Neither carries a licence fee.
What is the difference between Bluesky and CatchUp?
Bluesky is written in TypeScript and CatchUp in Kotlin. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Bluesky or CatchUp?
Choose Bluesky if you want the larger community (18,295 stars) or its MIT licence terms. Choose CatchUp if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.