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.
| Feature | Thunderbird Appointment | Cal.diy |
|---|---|---|
| Deploy effort | Under-an-hour setup | Read-the-docs project |
| Health score | 80 · Excellent | 96 · Excellent |
| 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 | ★ 552 | ★ 48,631 |
| First released | 2023 | None |
| Replaces | Calendly, Doodle | Calendly, Doodle |
What are Thunderbird Appointment and Cal.diy?
Thunderbird Appointment
Thunderbird Appointment is an open-source scheduling application that lets users share availability and let others book time slots. It integrates with CalDAV calendars and is built by the Thunderbird team.
- Availability sharing
- Bookable time slots
- CalDAV integration
- Built by Thunderbird
Cal.diy
Scheduling infrastructure for absolutely everyone.
- Self-hosted appointment scheduling
- Calendar and video integrations
- Team and round-robin booking
- Webhooks and API
Thunderbird Appointment vs Cal.diy: key differences
Thunderbird Appointment is written in Python, while Cal.diy is built with TypeScript. Licensing differs — MPL-2.0 for Thunderbird Appointment versus MIT for Cal.diy. Cal.diy has the considerably larger community, at 48,631 GitHub stars versus 552. Thunderbird Appointment lists first-class Docker deployment; Cal.diy does not.
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…
- Permissive MIT license
- Flexible scheduling workflows
- Multi-user support
Watch out for
- Setup can be involved
- Younger than established rivals
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.