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Zoiper vs Calls: catalog facts
Zoiper	Calls
Freemium Free softphone, with paid versions sold on the Zoiper site.	Free Free and open source under the GPL-3.0-or-later.
Windows, macOS, Linux, Android, iOS, Browser extension	Linux
Native apps on desktop and mobile TLS, SRTP and ZRTP call encryption	Handles both cellular and SIP calls Integrates with the GNOME desktop
Proprietary, with some features in paid editions Encryption depends on server support	Linux only SIP calling needs an account with a VoIP provider
Downloadable app, Browser extension	Downloadable app
Closed source	Open source
License not stated	License: GPL-3.0-or-later
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 24, 2026	Official website Full listing and sources Checked October 1, 2026

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