head to head · open source
Cal.com vs ical4j
Cal.com has 49,651 GitHub stars, 15,521 forks, 1,432 open issues and last shipped yesterday. ical4j has 841 stars, 225 forks, 162 open issues and last shipped 3 days ago. Cal.com leads on adoption by 5,804% (49,651 vs 841 stars). Cal.com is written in TypeScript under MIT; ical4j is written in Java under BSD-3-Clause. Cal.com has attracted 31% as many forks as stars, ical4j 27%. Cal.com 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
| Cal.com | ical4j | |
|---|---|---|
| GitHub stars | ★ 50K | ★ 841 |
| License | MIT | BSD-3-Clause |
| Written in | TypeScript | Java |
| Last push | 2026-11-02 | 2026-10-31 |
| Forks | ⑂ 16K | ⑂ 225 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Cal.com if
- You weight community size — 50K stars and counting
- You want the MIT license terms
- Your stack matches TypeScript
- You value the larger contributor base for long-term maintenance
pick ical4j if
- You want the ical4j feature set and don't need the biggest community
- You prefer the BSD-3-Clause license terms
- Your stack matches Java
- You evaluated both and ical4j fits your workflow better
About Cal.com
[!WARNING] Use at your own risk. Cal.diy is the open source community edition of Cal.com and it is intended for users who want to self host their own Cal.diy instance. It is strictly recommended for personal, non production use. Please review all installation and configuration steps carefully. Self hosting requires advanced knowledge of server administration, database management, and securing sensitive data. Proceed only if you are comfortable with these responsibilities. [!TIP] For any commercial and enterprise ready scheduling infrastructure, use Cal.com, not Cal.diy; hosted by us or get invited to on prem…
read the full Cal.com overview →
About ical4j
iCal4j iCalendar parser and object model [RFC2445]: [RFC2446]: [RFC2447]: [RFC5545]: [RFC5546]: [RFC6047]: [RFC6868]: [RFC7808]: [RFC7953]: [RFC7986]: [RFC7529]: [RFC9073]: [RFC9074]: [RFC9253]: [mavenrepo]: [Java Legacy Date Time Code]: [Introduction]: introduction [Setup]: setup [System requirements]: system requirements [Release downloads]: release downloads [Install with Maven]: install with maven [Install with Gradle]: install with gradle [Usage]: usage [Examples]: examples [References]: references [Specifications]: specifications [Configuration]: configuration [Compatibility Hints]: compatibility hints…
read the full ical4j overview →
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Frequently asked questions
Is Cal.com or ical4j more popular?
Cal.com has 49,651 GitHub stars and ical4j has 841. Cal.com has the larger community by that measure.
Are Cal.com and ical4j free?
Both are open source. Cal.com is licensed under MIT and ical4j under BSD-3-Clause. Neither carries a licence fee.
What is the difference between Cal.com and ical4j?
Cal.com is written in TypeScript and ical4j in Java. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Cal.com or ical4j?
Choose Cal.com if you want the larger community (49,651 stars) or its MIT licence terms. Choose ical4j if its feature set, stack or BSD-3-Clause licence fits better. Both are self-hostable.