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Delta Chat vs Threema: catalog facts
Delta Chat	Threema
Free Free and open source under the GPL 3.0. Free chatmail relays are provided, or use any…	Paid A one-time purchase is required. Business plans are separate.
Windows, macOS, Linux, Android, iOS	Windows, macOS, Linux, Android, iOS, Web
Works with any email account, or with a provided chatmail relay Reaches people who do not use Delta Chat at all	No phone number or email required; the ID is random Apps are open source and the company is based in Switzerland
Encryption only applies when the other side supports Autocrypt Email metadata such as subject and timing is visible to mail servers	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.