head to head · open source
Signal vs pki
Signal has 29,568 GitHub stars, 6,933 forks, 498 open issues and last shipped 4 days ago. pki has 514 stars, 160 forks, 46 open issues and last shipped yesterday. Signal leads on adoption by 5,653% (29,568 vs 514 stars). Signal is written in Kotlin under AGPL-3.0; pki is written in Java under GPL-2.0. Signal has attracted 23% as many forks as stars, pki 31%. pki 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 | pki | |
|---|---|---|
| GitHub stars | ★ 30K | ★ 514 |
| License | AGPL-3.0 | GPL-2.0 |
| Written in | Kotlin | Java |
| Last push | 2026-10-30 | 2026-11-02 |
| Forks | ⑂ 6.9K | ⑂ 160 |
| 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 pki if
- You want the pki feature set and don't need the biggest community
- You prefer the GPL-2.0 license terms
- Your stack matches Java
- You evaluated both and pki 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 pki
Dogtag PKI The Dogtag Certificate System is an enterprise class open source Certificate Authority (CA). It is a full featured system, and has been hardened by real world deployments. It supports all aspects of certificate lifecycle management, including key archival, OCSP and smartcard management, and much more. The Dogtag PKI suite provides the following subsystems: Certificate Authority (CA) Key Recovery Authority (KRA) Online Certificate Status Protocol (OCSP) Responder Token Key Service (TKS) Token Processing System (TPS) Automatic Certificate Management Environment (ACME) Responder Documentation The best…
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Frequently asked questions
Is Signal or pki more popular?
Signal has 29,568 GitHub stars and pki has 514. Signal has the larger community by that measure.
Are Signal and pki free?
Both are open source. Signal is licensed under AGPL-3.0 and pki under GPL-2.0. Neither carries a licence fee.
What is the difference between Signal and pki?
Signal is written in Kotlin and pki in Java. 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 pki?
Choose Signal if you want the larger community (29,568 stars) or its AGPL-3.0 licence terms. Choose pki if its feature set, stack or GPL-2.0 licence fits better. Both are self-hostable.