head to head · open source
Signal vs certspotter
Signal has 29,361 GitHub stars, 6,891 forks, 498 open issues and last shipped yesterday. certspotter has 1,175 stars, 104 forks, 18 open issues and last shipped 6 days ago. Signal leads on adoption by 2,399% (29,361 vs 1,175 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 | ★ 29K | ★ 1.2K |
| License | AGPL-3.0 | MPL-2.0 |
| Written in | Kotlin | Go |
| Last push | 2026-09-18 | 2026-09-13 |
| Forks | ⑂ 6.9K | ⑂ 104 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Signal if
- You weight community size — 29K 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 is a secure messaging application for Android devices that delivers private communication via end to end encryption. Developed by Signal Messenger, LLC, it operates within the broader Signal ecosystem, which includes official iOS and desktop clients. The app uses mobile data or Wi Fi to send and receive encrypted messages, voice calls, and video calls without relying on traditional SMS or telephony infrastructure.
read the full Signal overview →
About certspotter
Cert Spotter is a lightweight, open source Certificate Transparency log monitor from SSLMate that watches Certificate Transparency logs and alerts you when an SSL/TLS certificate is issued for any domain on your watch list, aimed at site operators, security teams, and PKI administrators who need to catch unauthorized certificates without operating a database.
read the full certspotter overview →
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Frequently asked questions
Is Signal or certspotter more popular?
Signal has 29,361 GitHub stars and certspotter has 1,175. 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 (29,361 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.