What does Mattermost replace?

Mattermost is a free alternative to Slack ($87/yr).

Is Mattermost open source?

Yes. Mattermost is licensed under AGPL-3.0 source / MIT compiled, an OSI-approved open-source license.

Yes (self-hosted server; web UI).

Yes. Mattermost is a server app you run on your own server.

A free, open-source alternative to Slack. Switching saves $87/yr at list price.

Checked Oct 17, 2026 · How we check

Self-hosted server

Open source · AGPL-3.0 source / MIT compiled Linux Self-hostable

mattermost/mattermost39.4k★last push Oct 17, 2026checked Oct 17, 2026

Self-host

Runs on your own Linux server. Setup docs are on mattermost.com.

What does Mattermost replace?: Mattermost is a free alternative to Slack ($87/yr).
Is Mattermost open source?: Yes. Mattermost is licensed under AGPL-3.0 source / MIT compiled, an OSI-approved open-source license.
Does Mattermost run on Linux?: Yes (self-hosted server; web UI).
Can you self-host Mattermost?: Yes. Mattermost is a server app you run on your own server.