Mattermost

What Is Mattermost?

Every organisation that has moved from email to team chat has, at some point, had the same uncomfortable conversation: who owns this data? With Slack, the answer is Salesforce, operating under US jurisdiction. With Microsoft Teams, it is Microsoft, subject to the CLOUD Act. For government agencies, defence contractors, financial institutions, and privacy-conscious European businesses, that answer is unacceptable.

Mattermost was built to resolve this tension. Originally created in 2016, the platform offers an open-source team messaging solution that can be deployed on your own infrastructure — on-premise, in a private cloud, or in an air-gapped environment with no internet connection. You control the servers, the encryption, the backup policies, and the access logs. No third party touches your data unless you choose to let them.

The company operates a European entity as Mattermost GmbH in Berlin, Germany, and offers EU-hosted cloud deployments for organisations that want managed hosting without US data transfers. The open-source codebase is publicly auditable, with an active contributor community and a plugin architecture that extends functionality without vendor lock-in.

Mattermost is not trying to be Slack for everyone. It is Slack for teams that cannot afford to let their communications live on someone else's servers — and increasingly, for DevOps and engineering teams that need their messaging platform to integrate directly into incident response, CI/CD pipelines, and operational workflows.

Key Features

Channels and Messaging

The core messaging experience follows the channel-based model popularised by Slack: public and private channels, direct messages, group conversations, threaded replies, emoji reactions, and rich text formatting with Markdown support. File sharing, image previews, and link unfurling work as expected. The interface is clean and functional, though it lacks some of the visual polish that Slack has spent years refining.

Search works across all channels and messages, with filters for date, sender, and file type. Message pinning, bookmarks, and saved posts help teams organise important information. For most day-to-day communication, the experience is comparable to Slack.

DevOps Playbooks

This is where Mattermost distinguishes itself most clearly. Playbooks are structured workflows for incident response, release management, and operational procedures. When an incident is triggered — manually or via an integration with monitoring tools like PagerDuty or Prometheus — a playbook creates a dedicated channel, assigns roles, runs through checklists, and tracks status updates in real time.

For engineering and operations teams, this eliminates the gap between "we detected a problem" and "we have a coordinated response." Playbooks are version-controlled, auditable, and can include automated actions like creating Jira tickets or sending notifications to stakeholders.

Boards

Mattermost Boards provides kanban-style project management directly within the platform. You can create boards for task tracking, sprint planning, or project management with custom properties, filters, and views. It is not as feature-rich as dedicated project management tools like Jira or Linear, but for teams that want lightweight task tracking alongside their messaging, it eliminates the need for a separate tool.

Self-Hosted Deployment

Mattermost's self-hosted edition can be installed on Linux servers, Kubernetes clusters, Docker environments, or cloud VMs. The deployment documentation is thorough, and the platform supports PostgreSQL and MySQL databases. High-availability configurations with load balancing and database replication are supported for enterprise deployments.

For regulated industries — healthcare, finance, government, defence — the ability to run a team messaging platform entirely within your own network perimeter is the deciding factor. No SaaS vendor can offer the same level of data control.

Plugin Marketplace

Mattermost's plugin system allows the community and third parties to extend the platform. Available integrations include Jira, GitLab, GitHub, Jenkins, CircleCI, Grafana, and many others. The API is comprehensive, supporting bots, slash commands, webhooks, and custom integrations. While the ecosystem is smaller than Slack's app directory, it covers the tools most engineering and operations teams rely on.

Pricing

Mattermost's pricing reflects its dual nature as both an open-source project and a commercial product.

The Free tier is genuinely generous: unlimited users, unlimited message history, core messaging features, and basic integrations. For small teams that need secure messaging without budget constraints, this is a legitimate option — particularly when self-hosted.

Professional at $10/user/month (cloud) adds guest accounts, advanced permissions, single sign-on (SAML, LDAP, OAuth), and the full playbooks feature set. This is the tier where Mattermost becomes a serious enterprise tool.

Enterprise is custom-priced and adds compliance features (data retention policies, custom terms of service, eDiscovery), high-availability support, and dedicated customer success management. Pricing is negotiated based on deployment size and requirements.

Self-hosting the open-source edition is free for unlimited users. The Team Edition includes core messaging and basic integrations. Enterprise features require a commercial licence even for self-hosted deployments.

EU Compliance & Privacy

Mattermost's EU compliance story is stronger than most open-source alternatives. The company operates Mattermost GmbH in Berlin, Germany, providing a European legal entity for contract and data processing purposes. Cloud deployments can be hosted in EU data centres, and self-hosted deployments give you complete control over data residency.

The platform includes data retention policies, message export for compliance archiving, and granular access controls. For organisations subject to GDPR, NIS2, or sector-specific regulations, the combination of an EU entity, EU hosting, and open-source auditability is a strong compliance package. SOC 2 Type II certification covers the cloud offering.

Who It's Best For

DevOps and engineering teams that need messaging integrated with incident response, CI/CD, and monitoring workflows. The playbooks feature is genuinely differentiated.

Security-conscious organisations — government, defence, finance, healthcare — that require self-hosted deployment with full data sovereignty.

European enterprises seeking a Slack alternative that can be hosted entirely within EU infrastructure under a European legal entity.

Open-source advocates who want an auditable, extensible communication platform without vendor lock-in.

The Verdict

Mattermost is not the easiest team chat to adopt, nor is it the most polished. The mobile apps lag behind Slack's, the free tier is basic compared to Slack's generous offering, and the ecosystem is smaller. But Mattermost solves a problem that Slack and Teams fundamentally cannot: it gives you complete ownership of your communication data. For organisations where data sovereignty is non-negotiable — and for DevOps teams that want their chat integrated into their operational workflow — Mattermost is the most capable open-source option available, with genuine EU credentials to back it up.

Frequently Asked Questions

Is Mattermost really free?

The open-source Team Edition is genuinely free for unlimited users when self-hosted. The cloud Free tier is also free with no time limit. Advanced features like SAML SSO, compliance exports, and enterprise-grade support require a paid plan or enterprise licence.

How difficult is it to self-host Mattermost?

A basic single-server deployment is straightforward for anyone with Linux administration experience — the documentation is thorough and well-maintained. High-availability deployments with load balancing and database clustering require more expertise. Docker and Kubernetes deployments are well-supported with official Helm charts.

Can Mattermost replace Slack for non-technical teams?

It can, but with caveats. The core messaging experience is comparable, and the interface is intuitive enough for non-technical users. However, Slack's app ecosystem is much larger, the onboarding experience is more polished, and features like Slack Connect for cross-organisation messaging have no direct equivalent. For mixed organisations, evaluate whether the DevOps and security benefits justify the trade-offs.

Does Mattermost support video calls?

Yes. Mattermost includes built-in audio and video calling for direct and group conversations. For larger meetings or more advanced video conferencing features, integrations with Zoom, Jitsi, and other platforms are available via plugins.

How does Mattermost handle data migration from Slack?

Mattermost provides official migration tools that import Slack workspace data including channels, messages, users, and files. The migration preserves message history and channel structure. Some Slack-specific features (custom workflows, app integrations) will need to be recreated using Mattermost equivalents.