head to head · open source
Zen vs certspotter
Zen has 4,347 GitHub stars, 145 forks, 14 open issues and last shipped 2 days ago. certspotter has 1,197 stars, 104 forks, 18 open issues and last shipped 7 days ago. Zen leads on adoption by 263% (4,347 vs 1,197 stars). Zen is written in Go under MIT; certspotter is written in Go under MPL-2.0. Zen has attracted 3% as many forks as stars, certspotter 9%. Zen 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
| Zen | certspotter | |
|---|---|---|
| GitHub stars | ★ 4.3K | ★ 1.2K |
| License | MIT | MPL-2.0 |
| Written in | Go | Go |
| Last push | 2026-11-03 | 2026-10-29 |
| Forks | ⑂ 145 | ⑂ 104 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Zen if
- You weight community size — 4.3K stars and counting
- You want the MIT license terms
- Your stack matches Go
- 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 Zen
Zen: Your Comprehensive Ad Blocker and Privacy Guard There is, simply, no way, to ignore privacy. Because a citizenry’s freedoms are interdependent, to surrender your own privacy is really to surrender everyone’s. Edward Snowden, Permanent Record Website • Mastodon • Bluesky • Discord • Documentation Zen is an open source system wide ad blocker and privacy guard for Windows, macOS, and Linux. It works by setting up a proxy that intercepts HTTP requests from all applications, and blocks those serving ads, tracking scripts that monitor your behavior, malware, and other unwanted content. By operating at the system…
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 Zen or certspotter more popular?
Zen has 4,347 GitHub stars and certspotter has 1,197. Zen has the larger community by that measure.
Are Zen and certspotter free?
Both are open source. Zen is licensed under MIT and certspotter under MPL-2.0. Neither carries a licence fee.
What is the difference between Zen and certspotter?
Zen is written in Go 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, Zen or certspotter?
Choose Zen if you want the larger community (4,347 stars) or its MIT licence terms. Choose certspotter if its feature set, stack or MPL-2.0 licence fits better. Both are self-hostable.