Mattermost vs Slack

Self-host swap-in for Slack. · Self-host Slack · Mattermost on os-alt

Mattermost is one of the open-source self-host replacements for Slack — license AGPL-3.0 (Team Edition) / Source Available (Enterprise), 15min docker-compose to stand up, and $5 vps handles ~50 daily-active users on the postgres + mattermost server combo. Compare against Slack's $8.75/user/mo on Pro; message history capped on free tier below.

	Mattermostopen-source	Slackpaid SaaS
Category	Team chat	Team chat
License / pricing	`AGPL-3.0 (Team Edition) / Source Available (Enterprise)`	$8.75/user/mo on Pro; message history capped on free tier
Starting price	$0 self-host	$8.75/user/mo
GitHub	mattermost/mattermost ★ 36.7k · last commit todayalive	closed source
Setup time	15min docker-compose	SaaS — sign up + bill
Monthly cost	$5 VPS handles ~50 daily-active users on the Postgres + Mattermost server combo.	from $8.75/user/mo ($8.75/user/mo on Pro; message history capped on free tier)

Switching from Slack to Mattermost

Slack → Workspace settings → Import/Export → Export. Get the .zip. In Mattermost, run `mattermost import slack <team> <file.zip>` from the CLI. Preserves channels, users, message history, and most file uploads. Threads come over but emoji reactions are partial.

Full step-by-step migration guide →

Good fit for: Engineering teams that want Slack-shaped chat with code blocks and integrations.
Weak at: Voice/video huddles are weaker than Slack's; mobile clients are slower.
License note: Team Edition is AGPL and freely self-hostable; Enterprise features (LDAP groups, compliance export) need a license.

Other open-source self-host alternatives to Slack

Rocket.Chat
MIT15min docker-compose (Mongo + Rocket.Chat)$10 VPS — Mongo is the heavier process; tight on $5.
Zulip
Apache-2.030-60min (their installer script on Ubuntu 22.04)$10 VPS minimum (their installer wants 2GB+ RAM).

Mattermost also replaces

Discord— Community / voice chat
Microsoft Teams— Team chat + video meetings

In a terminal? npx os-alt slack prints Slack's self-host options — how the CLI works →

FAQ

Is Mattermost a free alternative to Slack?

Yes — Mattermost is open source under AGPL-3.0 (Team Edition) / Source Available (Enterprise). Self-host cost: $5 VPS handles ~50 daily-active users on the Postgres + Mattermost server combo.. Slack starts at $8.75/user/mo ($8.75/user/mo on Pro; message history capped on free tier).

How long does Mattermost take to set up vs Slack?

Self-hosting Mattermost: 15min docker-compose. Slack is a hosted SaaS — sign up and you're in.

What is Mattermost good at, and what is it weak at?

Good fit for: Engineering teams that want Slack-shaped chat with code blocks and integrations.. Weak at: Voice/video huddles are weaker than Slack's; mobile clients are slower..