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Fossify Calendar vs Microsoft Outlook for iOS and Android: catalog facts
Fossify Calendar	Microsoft Outlook for iOS and Android
Free Free and open source with no ads.	Freemium The app is a free download; Microsoft 365 plans are sold separately.
Android	Android, iOS
No ads or tracking Syncs with Google, Outlook, Nextcloud and Exchange calendars	Email, calendar and contacts in one app Available on both iOS and Android phones and tablets
Android only Sync relies on accounts already set up on the device	Closed source Closely tied to Microsoft's services and plans
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0-only	License not stated
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 23, 2026

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