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Duetto vs Signal: catalog facts
Duetto	Signal
Free Free and open source under the GPL 3.0 or later.	Free Free; developed by a nonprofit funded by grants and donations
Android, Self-hosted	Android, iOS, Windows, macOS, Linux
End-to-end encrypted audio and video Always-on channel with no calling step	End-to-end encryption on every message and call using the open source Signal Protocol No ads, affiliate marketers or tracking
Limited to two people by design Very new project with little track record	Requires a phone number that can receive an SMS or phone call to register Desktop app requires Signal to be installed on a phone first
Downloadable app, Self-hosted	Downloadable app
Open source	Open source
License: GPL-3.0-or-later	License: AGPL-3.0
Not stated if an account is needed	Account needed
Needs internet	Needs internet
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked September 20, 2026

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