head to head · open source
Mastodon vs CatchUp
Mastodon has 50,299 GitHub stars, 7,498 forks, 4,525 open issues and last shipped yesterday. CatchUp has 2,101 stars, 210 forks, 31 open issues and last shipped 3 days ago. Mastodon leads on adoption by 2,294% (50,299 vs 2,101 stars). Mastodon is written in Ruby under AGPL-3.0; CatchUp is written in Kotlin under Apache-2.0. Mastodon has attracted 15% as many forks as stars, CatchUp 10%. Mastodon 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
| Mastodon | CatchUp | |
|---|---|---|
| GitHub stars | ★ 50K | ★ 2.1K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | Ruby | Kotlin |
| Last push | 2026-09-17 | 2026-09-15 |
| Forks | ⑂ 7.5K | ⑂ 210 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Mastodon if
- You weight community size — 50K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Ruby
- 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 Mastodon
Mastodon is a free, open source, self hosted social network server built on ActivityPub that lets anyone run a microblogging community which interoperates with the wider Fediverse, and it is aimed at individuals, communities, and organisations that want to own their social graph instead of renting it from a platform.
read the full Mastodon 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 Mastodon or CatchUp more popular?
Mastodon has 50,299 GitHub stars and CatchUp has 2,101. Mastodon has the larger community by that measure.
Are Mastodon and CatchUp free?
Both are open source. Mastodon is licensed under AGPL-3.0 and CatchUp under Apache-2.0. Neither carries a licence fee.
What is the difference between Mastodon and CatchUp?
Mastodon is written in Ruby 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, Mastodon or CatchUp?
Choose Mastodon if you want the larger community (50,299 stars) or its AGPL-3.0 licence terms. Choose CatchUp if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.