Mattermost, Slack, and Rocket.Chat comparison

The cost of cloud-based messaging

Slack provides a managed service that stores all communication history on Amazon Web Services. For many businesses, the cost of this convenience is high. Slack’s paid plans cost $7.25 per user per month, and users seeking to unlock features like single sign-on or enterprise scalability must pay more than $350 per user per year. A 15-person team pays over $1,300 annually for Slack. Slack also has an extensive app directory with over 2,000 integrations including syntax coloring, @mentions, and emoji reactions. If you use the free plan, Slack deletes any messages older than 90 days. Mattermost is an open-source, self-hosted alternative that functions as a Slack replacement. Mattermost provides unlimited message history and unlimited users in its free team edition. You control the PostgreSQL database on your own server. For organizations that handle sensitive client data in regulated industries, the ability to host Mattermost on their own infrastructure simplifies compliance by keeping all messages on internal hardware. Mattermost provides encryption at rest and encryption in transit. Mattermost integrates with Jira, GitHub, GitLab, ServiceNow, and PagerDuty via REST API, webhooks, and slash commands. You can also use custom slash commands and bots. Mattermost runs on your own hardware, which gives you complete control over your communication data. This eliminates the risk of losing institutional memory when a third-party provider changes its pricing or suffers an outage. If you already know the basics of self-hosting, you know that managing a server requires predictable effort rather than zero effort.

Comparing Mattermost and Rocket.Chat

Rocket.Chat and Mattermost both provide open-source, self-hosted messaging. Rocket.Chat has 46,213 GitHub stars, while Mattermost has 39,261. Rocket.Chat includes video calls and omnichannel communication out of the box. You must use plugins to get advanced features like video calls in Mattermost. Rocket.Chat provides native Matrix federation and is compatible with XMPP. Rocket.Chat also allows you to deploy using Docker, Kubernetes, Launchpad, or cloud providers for custom setups. Rocket.Chat is designed for mission-critical, zero-trust team collaboration. Mattermost focuses on internal communication, while Rocket.Chat extends its abilities to include external communication with customers, suppliers, partners, and vendors. Rocket.Chat is highly customizable, allowing you to brand and theme the interface. Mattermost has limited branding and customization options. Rocket.Chat has a more complex interface that may have a steeper learning curve. Mattermost uses a simpler interface that is reminiscent of Slack. Rocket.Chat uses more system resources, whereas Mattermost runs efficiently even on modest servers. Rocket.Chat is designed to support several hundred users, but some users report difficulty scaling past 1,000 users. Mattermost supports at least 60,000 concurrent users and 60 million posts in the database. How do teams manage the transition from the free Team edition to the Entry edition without losing access to critical data?

Versioning and deployment constraints

Mattermost Platform 12.0 includes Attribute Management, channel labels, and improved direct-message calling. The release also adds Ranked and Hierarchical Attributes. Mattermost Platform 11.11.0 includes a Data Spillage: Exposure Radius Report. Support for Mattermost Server v10.11 Extended Support Release ended on August 15, 2026. Mattermost Desktop App v6.3.1, released on October 15, 2026, contains medium severity security fixes. This update fixes a malformed SiteURL crash and an issue where the Calls widget could crash the app when resized. Mattermost Desktop App v6.3.0, released on August 14, 2026, updated the Chromium minimum supported version to 150+. Mattermost can be deployed via Docker Compose in about 10 minutes. You can also add it behind a reverse proxy using SSL. The Mattermost Entry edition imposes a 10,000 message restriction on a per-channel basis. This restriction means messages sent before a certain date can be hidden. You can use the official Docker image to include everything needed for a deployment. Mattermost integrates with various tools through its Integrations Directory. Users can run AI agents using the Ollama API for smooth performance. Mattermost Desktop App v6.2.1, released in June 2026, improved the reliability of the downloads handler when handling unexpected network responses. Mattermost’s user limit of 250 is a suggestion, not a hard limit.