Thunderbird Appointment vs Cal.diy
A side-by-side comparison of two self-hosted calendar & contacts options — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
Thunderbird Appointment
Self-hostable scheduling tool for booking meetings
VS
Cal.diy
Online appointment scheduling system
| Feature | Thunderbird Appointment | Cal.diy |
|---|---|---|
| Category | Calendar & Contacts | Calendar & Contacts |
| License | MPL-2.0 | MIT |
| Language | Python | TypeScript |
| Setup difficulty | Medium | Medium |
| Min. RAM | 512 MB | 512 MB |
| Deployment | docker, source | bare-metal |
| GitHub stars | ★ 547 | ★ 47,334 |
| First released | 2023 | 2026 |
| Replaces | Calendly, Doodle | — |
Why pick each one
Choose Thunderbird Appointment if…
- Released under the MPL-2.0 license
- First-class Docker support for quick deployment
- Written in Python
- Lightweight — runs in 512 MB RAM
Choose Cal.diy if…
- Released under the MIT license
- Mature project with 47.3k GitHub stars
- Written in TypeScript
- Lightweight — runs in 512 MB RAM
Frequently asked questions
Is Thunderbird Appointment or Cal.diy better?
Neither is universally better. Cal.diy has the larger community; both share a medium setup difficulty, so the decision comes down to features and licensing.
Are Thunderbird Appointment and Cal.diy free and open-source?
Yes. Thunderbird Appointment is licensed under MPL-2.0 and Cal.diy under MIT. Both can be self-hosted at no software cost.
Can I run Thunderbird Appointment and Cal.diy with Docker?
Thunderbird Appointment: yes. Cal.diy: check the project docs for container support.