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Mattermost vs Flock: catalog facts
Mattermost	Flock
Freemium The desktop client is free and open source. The Mattermost server has a free self-hosted…	Freemium Sign-up is self-serve; check the site for current plans.
Windows, macOS, Linux	Web
The server is self-hosted, so message data never leaves your infrastructure Server dropdown lets one client connect to several Mattermost instances	Channels for organising team discussion Built-in voice and video calls with screen sharing
Needs a Mattermost server, which is real infrastructure to run Electron, so memory use is high for a chat client	Proprietary hosted service; data lives on the vendor's servers Aimed at organisations rather than personal use
Downloadable app	Downloadable app, Web application, Hosted service
Open source	Closed source
License: Apache-2.0	License not stated
Account needed	Account needed
Needs internet	Needs internet
Official website Full listing and sources Checked September 21, 2026	Official website Full listing and sources Checked September 24, 2026

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