Citadel vs Calcom Calendar
A side-by-side comparison of two self-hosted groupware options — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
Citadel
All-in-one groupware, mail and collaboration server
VS
Calcom Calendar
Open-source scheduling and appointment booking platform
| Feature | Citadel | Calcom Calendar |
|---|---|---|
| Category | Groupware | Groupware |
| License | GPL-3.0 | AGPL-3.0 |
| Language | C | TypeScript |
| Setup difficulty | Medium | Medium |
| Min. RAM | 512 MB | 1,024 MB |
| Deployment | bare-metal, source | docker, bare-metal, source |
| GitHub stars | ★ 100 | ★ 47,334 |
| First released | 1987 | 2021 |
| Replaces | Microsoft Exchange, Microsoft 365 | Calendly, Doodle |
Why pick each one
Frequently asked questions
Is Citadel or Calcom Calendar better?
Neither is universally better. Calcom Calendar has the larger community; both share a medium setup difficulty, so the decision comes down to features and licensing.
Are Citadel and Calcom Calendar free and open-source?
Yes. Citadel is licensed under GPL-3.0 and Calcom Calendar under AGPL-3.0. Both can be self-hosted at no software cost.
Can I run Citadel and Calcom Calendar with Docker?
Citadel: check the project docs for container support. Calcom Calendar: yes.