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OneCal vs CalSync: catalog facts
OneCal	CalSync
Freemium Free to start with no credit card required.	Free Free and open source under the GPL-3.0 licence, with no subscription.
Android, iOS, Web	Android
Real-time sync across Google, Outlook and iCloud Control over which event details are copied	Works entirely on the device Custom names for copied events
Requires granting a third-party service access to your calendars Hosted only, with no self-hosted option	Android only Only syncs calendars already present on the device
Downloadable app, Hosted service	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0
Account needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.