Citadel vs Horde Groupware
A side-by-side comparison of two self-hosted groupware options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Citadel | Horde Groupware |
|---|---|---|
| Deploy effort | Read-the-docs project | Read-the-docs project |
| Status | Actively maintained | Archived |
| Category | Groupware | Groupware |
| License | GPL-3.0 | GPL-2.0 |
| Language | C | PHP |
| Setup difficulty | Medium | Hard |
| Min. RAM | 512 MB | 512 MB |
| Deployment | bare-metal, source | bare-metal, source |
| GitHub stars | ★ 100 | ★ 242 |
| First released | 1987 | 2003 |
| Replaces | Microsoft Exchange, Microsoft 365 | Microsoft Exchange |
What are Citadel and Horde Groupware?
Citadel
Citadel is a mature, all-in-one collaboration suite that integrates email, calendaring, address books, instant messaging, and bulletin boards. It is designed for easy installation and minimal maintenance.
- Integrated mail and calendar
- Built-in groupware web client
- Instant messaging and forums
- Easy installer
Horde Groupware
Horde Groupware is a collaboration suite built on the Horde framework that combines webmail, calendar, address book, tasks, and notes. It is a long-running PHP groupware project for teams.
- Webmail with calendar
- Shared address books
- Tasks and notes
- Modular Horde framework
Citadel vs Horde Groupware: key differences
The biggest difference is maintenance: Horde Groupware's repository is archived and no longer developed, while Citadel is actively maintained. Citadel is written in C, while Horde Groupware is built with PHP. Licensing differs — GPL-3.0 for Citadel versus GPL-2.0 for Horde Groupware. Citadel is the more established project (first released 1987), while Horde Groupware arrived in 2003. Horde Groupware has the considerably larger community, at 242 GitHub stars versus 100.
Why pick each one
Choose Citadel if…
- Single-package setup
- Low resource needs
Watch out for
- Niche project
- Old-fashioned UI
Choose Horde Groupware if…
- Released under the GPL-2.0 license
- Written in PHP
- Lightweight — runs in 512 MB RAM
Frequently asked questions
Is Citadel or Horde Groupware better?
Neither is universally better. Horde Groupware has the larger community, while Citadel is simpler to set up (medium difficulty). Choose based on the comparison table above and your own setup.
Are Citadel and Horde Groupware free and open-source?
Yes. Citadel is licensed under GPL-3.0 and Horde Groupware under GPL-2.0. Both can be self-hosted at no software cost.
Can I run Citadel and Horde Groupware with Docker?
Citadel: check the project docs for container support. Horde Groupware: check the project docs for container support.