head to head · open source
Signal vs certspotter
Signal has 29,568 GitHub stars, 6,933 forks, 498 open issues and last shipped 5 days ago. certspotter has 1,195 stars, 104 forks, 18 open issues and last shipped 6 days ago. Signal leads on adoption by 2,374% (29,568 vs 1,195 stars). Signal is written in Kotlin under AGPL-3.0; certspotter is written in Go under MPL-2.0. Signal has attracted 23% as many forks as stars, certspotter 9%. Signal 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
| Signal | certspotter | |
|---|---|---|
| GitHub stars | ★ 30K | ★ 1.2K |
| License | AGPL-3.0 | MPL-2.0 |
| Written in | Kotlin | Go |
| Last push | 2026-10-30 | 2026-10-29 |
| Forks | ⑂ 6.9K | ⑂ 104 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Signal if
- You weight community size — 30K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Kotlin
- You value the larger contributor base for long-term maintenance
pick certspotter if
- You want the certspotter feature set and don't need the biggest community
- You prefer the MPL-2.0 license terms
- Your stack matches Go
- You evaluated both and certspotter fits your workflow better
About Signal
Signal Android Signal is a simple, powerful, and secure messenger that uses your phone's data connection (WiFi/4G/5G) to communicate securely. Millions of people use Signal every day for free and instantaneous communication anywhere in the world. Send and receive high fidelity messages, participate in HD voice/video calls, and explore a growing set of new features that help you stay connected. Signal’s advanced privacy preserving technology is always enabled, so you can focus on sharing the moments that matter with the people who matter to you. Currently available on the Play Store and signal.org. Also available…
read the full Signal overview →
About certspotter
Cert Spotter Certificate Transparency Monitor Open Source Edition Cert Spotter is a Certificate Transparency log monitor from SSLMate that alerts you when an SSL/TLS certificate is issued for one of your domains. Cert Spotter is easier to use than other open source CT monitors, since it does not require a database. It's also more robust, since it uses a special certificate parser that ensures it won't miss certificates. Cert Spotter is available as a hosted service by SSLMate that also provides monitoring for expiring and incorrectly installed certificates, Slack notifications, and a Web dashboard for tracking…
read the full certspotter overview →
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Frequently asked questions
Is Signal or certspotter more popular?
Signal has 29,568 GitHub stars and certspotter has 1,195. Signal has the larger community by that measure.
Are Signal and certspotter free?
Both are open source. Signal is licensed under AGPL-3.0 and certspotter under MPL-2.0. Neither carries a licence fee.
What is the difference between Signal and certspotter?
Signal is written in Kotlin and certspotter in Go. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Signal or certspotter?
Choose Signal if you want the larger community (29,568 stars) or its AGPL-3.0 licence terms. Choose certspotter if its feature set, stack or MPL-2.0 licence fits better. Both are self-hostable.