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Element vs Mattermost: catalog facts
Element	Mattermost
Freemium The client is free and open source under the AGPL 3.0. Element Matrix Services sells…	Freemium The desktop client is free and open source. The Mattermost server has a free self-hosted…
Windows, macOS, Linux, Android, iOS, Web, Self-hosted	Windows, macOS, Linux
End-to-end encryption with cross-signed device verification Federated, so you can run your own server and still reach everyone	The server is self-hosted, so message data never leaves your infrastructure Server dropdown lets one client connect to several Mattermost instances
Encryption key management confuses people the first time they log in on a new device Heavy on memory for a chat app, and slow with many large rooms	Needs a Mattermost server, which is real infrastructure to run Electron, so memory use is high for a chat client
Downloadable app	Downloadable app
Open source	Open source
License: AGPL-3.0	License: Apache-2.0
Account needed	Account needed
Works offline	Needs internet
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 21, 2026

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