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Session vs Threema: catalog facts
Session	Threema
Free Free and open source under the GPL 3.0, run by the Session Technology Foundation.	Paid A one-time purchase is required. Business plans are separate.
Windows, macOS, Linux, Android, iOS	Windows, macOS, Linux, Android, iOS, Web
No phone number or email needed; the account is a random ID Onion routing hides your address from recipients and from the network	No phone number or email required; the ID is random Apps are open source and the company is based in Switzerland
Losing your recovery phrase means losing the account with no reset Delivery can be slower than a centralised messenger	A one-time purchase is required for each platform Smaller user base than the mainstream encrypted messengers
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: AGPL-3.0
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 September 21, 2026	Official website Full listing and sources Checked September 22, 2026

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