Mattermost vs Slack

At a glance

Slack has a free plan. We haven't confirmed one for Mattermost.
Mattermost offers a free trial (length not stated). We haven't confirmed one for Slack.
Slack's lowest paid plan is Pro at $8.75 per user per month, paid monthly, as of October 20, 2026.
Both are available on Windows, macOS, Linux, iOS, Android and API.
Only Mattermost lists Web.
Both work with Zoom.
Both list SSO.
Only Slack lists SOC 2, ISO 27001, GDPR and HIPAA.
Both have a public API.
Mattermost can be self-hosted. We haven't confirmed that for Slack.

From each tool's own website, checked on the dates below, and from published reviews.

From the facts checked for both tools, not from opinion. A fact we haven't confirmed for one of them is never counted.

Integration with Google Drive, Salesforce or Asana. We haven't found them on Mattermost's website.
SOC 2, ISO 27001, GDPR or HIPAA. We haven't found them on Mattermost's website.

No reviews yet

Nobody has reviewed Mattermost yet. Its rating shows once it has 3 reviews.

No reviews yet

Nobody has reviewed Slack yet. Its rating shows once it has 3 reviews.

What it does: MattermostZero-trust collaboration, automation and AI in private cloud, self-hosted, and air-gapped environments; SlackAll your people and AI agents working together
Free plan: MattermostNot confirmed; SlackYes
Pricing: MattermostNot confirmed; SlackPer user, monthly
Paid plans from: Mattermost

From the platforms and integrations each website lists.

Both

Only Mattermost

Only SlackNothing else listed

Both

Reviewers who say they used one of these before the other.

No reviewer has said they moved between Mattermost and Slack yet.

Your review makes this comparison better for the next person. Review Mattermost or review Slack.