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Threema vs Session: catalog facts
Threema	Session
Paid A one-time purchase is required. Business plans are separate.	Free Free and open source under the GPL 3.0, run by the Session Technology Foundation.
Windows, macOS, Linux, Android, iOS, Web	Windows, macOS, Linux, Android, iOS
No phone number or email required; the ID is random Apps are open source and the company is based in Switzerland	No phone number or email needed; the account is a random ID Onion routing hides your address from recipients and from the network
A one-time purchase is required for each platform Smaller user base than the mainstream encrypted messengers	Losing your recovery phrase means losing the account with no reset Delivery can be slower than a centralised messenger
Downloadable app	Downloadable app
Open source	Open source
License: AGPL-3.0	License: GPL-3.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 21, 2026

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