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Microsoft Outlook vs Calendars by Readdle: catalog facts
Microsoft Outlook	Calendars by Readdle
Freemium Free app and account available; Microsoft 365 plans add paid features and Office apps.	Free Free to download from the App Store and as a Mac download.
Windows, macOS, Android, iOS, Web	macOS, iOS
Email, calendar and contacts for multiple accounts in one app Available on desktop, mobile and web	Natural language event creation Calendars and tasks in one view
Closed source and tied to Microsoft services Some features, including Copilot, require a paid plan	Apple platforms only No Windows or Android version
Downloadable app, Web application	Downloadable app
Closed source	Closed source
License not stated	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked October 1, 2026

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