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Synology ChatMattermost
Free

License-free, but it requires a Synology NAS to host the server.

 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
  • Messages stay on your own NAS
  • Optional end-to-end encryption for conversations or channels
  • The server is self-hosted, so message data never leaves your infrastructure
  • Server dropdown lets one client connect to several Mattermost instances
  • Only runs on Synology NAS hardware
  • Closed source
  • Needs a Mattermost server, which is real infrastructure to run
  • Electron, so memory use is high for a chat client
Downloadable app, Web application, Self-hosted Downloadable app
Closed source Open source
License not stated License: Apache-2.0
Account needed Account needed
Not stated if it works offline Needs internet

Checked October 1, 2026

Checked September 21, 2026

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