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Best Offline-First Calendar & Contacts for self-hosting

The 6 best Offline-First calendar & contacts you can self-host, ranked by community traction.

EasyMedium

binarysource

khal

Calendar & Contacts

Command-line calendar built on CalDAV

Replaces Google Calendar

★ 3k Medium setup MIT

Tasks.org CalDAV Sync

Calendar & Contacts

Open-source calendar and task sync client for Android

Replaces Google Calendar Sync, iCloud sync

★ 2.8k Easy setup GPL-3.0

vdirsyncer

Calendar & Contacts

Synchronize calendars and contacts via CalDAV/CardDAV

Replaces iCloud sync

★ 1.9k Medium setup BSD-3-Clause

calcurse

Calendar & Contacts

Text-based calendar and scheduling application

Replaces Google Calendar

★ 1.3k Easy setup BSD-2-Clause

Decsync Calendar Sync

Calendar & Contacts

File-based calendar and contacts synchronization

Replaces Google Calendar

★ 696 Medium setup GPL-3.0

KOrganizer

Calendar & Contacts

Calendar and scheduling component of KDE Kontact

Replaces Outlook Calendar

★ 100 Medium setup GPL-2.0

Every option here is open-source and self-hostable, tagged Offline-First within the calendar & contacts category. Compare them on the individual app pages for setup difficulty and resource requirements.