Mattermost and Slack both give teams channels, threads, direct messages, calls and integrations. The main difference is who runs the service. Slack is a hosted service that Slack operates, with options to choose where certain data is stored and, on Enterprise plans, to use your own encryption keys. Mattermost is built to be self-hosted, so the servers, database and files sit on infrastructure you control, and so does the work of running them.
Choose Slack when you want a managed service with a large app directory and little to operate. Choose Mattermost when policy, contracts or network design require messaging to run inside your own environment, including disconnected networks.
OPS resells, deploys and supports both Mattermost and Slack through its Collaboration & Workplace practice. This guide is based on each vendor's published documentation, checked on October 28, 2026. Plans and features change, so confirm details with the vendor before you buy.
At a glance
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| Area | Mattermost | Slack |
|---|---|---|
| Who runs it | You, or a partner, on your infrastructure | Slack |
| Deployment | Linux, Docker, Kubernetes, private cloud, air-gapped | Slack-hosted plans |
| Default data location | Wherever you host it | United States |
| Regional storage | Your choice of site | Data residency on Business+ and Enterprise |
| Customer-held keys | Your own infrastructure | Enterprise Key Management add-on, keys in AWS KMS |
| Free option | Team Edition and Entry | Free plan with 90 days of history |
| Model | Open core with paid editions | Subscription plans |
Deployment and who runs the service
Mattermost's deployment planning guide describes three main paths:
- Kubernetes, which Mattermost recommends for production, with high availability and automated updates and rollbacks.
- Direct installation on Linux servers, for full control.
- Docker containers, which Mattermost describes as suitable for smaller deployments only, with no high availability support.
The server is written in Go, stores data in PostgreSQL and keeps files on local disk, NFS or S3-compatible storage. Mattermost's pricing page lists air-gapped and DDIL (disconnected, denied, intermittent and limited) environments in its Enterprise Advanced package. Its editions page also mentions a dedicated virtual secure Cloud add-on with a 99.9% uptime SLA, so a hosted route exists, but the product is designed around self-hosting.
With Slack, you choose a plan and Slack runs the infrastructure, updates and scaling.
Data location and encryption keys
If you do not use data residency, Slack stores your data in the US. Data residency for Slack lets Business+ and Enterprise customers store certain data at rest in one region. Options include Frankfurt, Paris, Stockholm, Zurich, London, Montreal, Tokyo, Mumbai, Singapore, Seoul, Sydney and São Paulo. Read the scope carefully:
- Stored in region: messages, canvases, snippets, uploaded files, the search index and app-generated content.
- May be stored elsewhere: member profiles, workspace and channel membership, seat and usage data, and analytics logs.
- Existing data stays in the US unless you ask Slack to migrate it.
Slack states that data residency changes only the storage location, and that Slack continues to process the data under your agreement.
Slack Enterprise Key Management (EKM) is a security add-on for Enterprise plans. It encrypts messages, files and the search index with your own keys, stored in Amazon's Key Management Service, and lets you revoke access at a granular level. Profiles, channel names and file names stay encrypted with Slack-controlled keys.
With Mattermost, data location follows your hosting choice. The database, configuration and files live where you deploy them, and key management follows your own infrastructure standards.
Identity, admin and compliance
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| Control | Mattermost | Slack |
|---|---|---|
| MFA | Professional package | Two-factor authentication on all plans |
| SSO | SAML, OpenID Connect and OAuth 2.0 in the Professional package | Google OAuth on Pro, SAML on Business+, multiple SAML setups on Enterprise+ |
| Directory | AD/LDAP user sync in Professional, AD/LDAP group sync in Enterprise | SCIM provisioning (Free and Pro need a connected Salesforce org) |
| Admin roles | Granular system permissions in Professional, delegated admin roles in Enterprise | Custom roles on Enterprise+ |
| Audit logs | Granular audit logs with export in Enterprise | Audit logs and Audit Logs API on Enterprise plans |
| Compliance | eDiscovery, compliance export and custom retention in Enterprise | Full exports on Business+ by application, legal holds and Discovery API on Enterprise+ |
Sources for this table are Mattermost's pricing and editions pages and Slack's pricing, plans and features, audit logs and export pages. Slack retains Enterprise audit logs for up to two years, so export them if you need longer retention.
Integrations and apps
Slack's pricing page lists more than 2,600 apps in the Slack App Directory, including Salesforce, Jira and Google Drive. The Free plan allows 10 apps. Paid plans add Workflow Builder and let you deploy custom functions on Slack's infrastructure.
Mattermost offers a plugin platform, REST API, MCP server, webhooks and slash commands, plus prepackaged integrations for tools such as Jira, GitHub, GitLab and Zoom. Its platform overview also lists ServiceNow, PagerDuty and SIEM and SOAR tools, and integrations with internal and legacy systems. Check that every app your teams rely on has a Mattermost path before you commit.
Licensing and editions
Mattermost calls itself open core. According to its editions page:
- Team Edition is free, open source and MIT-licensed, for small teams under 250 users that do not need SSO. Mattermost does not recommend it for government or sensitive commercial workloads.
- Enterprise Edition is a commercial binary. Without a subscription it runs as Entry, which is free but limits message history to 10,000 messages and excludes compliance features and high availability. Mattermost suggests Entry for teams under 50 users.
- Paid plans are Professional (aimed at teams of up to 250 users), Enterprise and Enterprise Advanced.
Slack offers Free, Pro, Business+ and Enterprise+ plans.
Operations burden
Self-hosting moves operational work to your team or a partner:
- Patching. Mattermost's release policy asks self-hosted admins to plan upgrades before release life cycles end. Extended Support Releases arrive every nine months and are supported for 12 months.
- Database. PostgreSQL needs its own upgrades, as Mattermost raises its minimum supported version over time.
- Backups. The backup guide covers the database, configuration and files separately and says a clean backup requires stopping Mattermost. Active/passive disaster recovery is supported, active/active is not.
- Scaling. High availability and horizontal scaling need an Enterprise subscription and a cluster deployment.
- Edge services. You also run the reverse proxy, TLS certificates and monitoring.
With Slack, your team still owns plan choice, identity setup, retention settings and app approvals, but not servers.
When each fits
Mattermost tends to fit when:
- Data must stay on infrastructure you own, in a set country or on an isolated network.
- Security, DevOps or operations teams want chat wired into internal tools.
- You already run Linux, PostgreSQL or Kubernetes and have people to operate them.
Slack tends to fit when:
- You want a managed service with no servers to run.
- One of Slack's residency regions meets your location requirement.
- Teams depend on apps from Slack's directory or work closely with outside organizations.
Decision checklist
- Location rules. Write down where data must be stored and who may operate the system. Compare that with Slack's regions and the data it keeps outside them.
- Key control. Decide whether you need customer-held keys. In Slack, that means an Enterprise plan plus EKM.
- Identity. Confirm the SSO protocol, directory sync and MFA policy you need, and which plan provides them.
- Compliance. List retention, legal hold, eDiscovery and audit needs, then map them to editions.
- Integrations. Inventory current apps, bots and workflows and confirm each has a path.
- Operations. If you self-host, name who patches, backs up, monitors and scales, and test a restore.
- Total cost. Compare subscriptions plus hosting, staff time, support and migration.
Common questions
Is Mattermost a self-hosted Slack alternative?
Yes. Mattermost describes itself as an open core, self-hosted platform with channels, threads, calls, file sharing and integrations. It runs on Linux, Docker or Kubernetes on infrastructure you choose.
Can Slack be self-hosted?
Slack's published plans are hosted by Slack. Data residency and Enterprise Key Management give you more control over storage location and keys, while Slack continues to run the service.
Does Slack data residency keep all data in my region?
No. Slack lists data that may be stored outside your region, such as member profiles and channel membership. Existing data stays in the US unless you request a migration.
Is Mattermost free?
Team Edition is free and open source for small teams that do not need SSO. Enterprise Edition runs free as Entry, with limits. Paid subscriptions add support and remove those limits.
Does OPS work with both products?
Yes. OPS resells, deploys and supports both Mattermost and Slack, so it can compare them against your requirements rather than steer you to one.
Talk through your requirements
The OPS Collaboration & Workplace practice deploys and supports both platforms, with identity, retention and governance set up from the start. See the Mattermost and Slack pages, or bring your location, compliance and integration requirements and OPS can help you choose.
Sources
- Mattermost, Server deployment planning. Checked October 28, 2026.
- Mattermost, Editions and offerings. Checked October 28, 2026.
- Mattermost, Pricing. Checked October 28, 2026.
- Mattermost, Platform overview. Checked October 28, 2026.
- Mattermost, Release policy. Checked October 28, 2026.
- Mattermost, Backup and disaster recovery. Checked October 28, 2026.
- Slack, Data residency for Slack. Checked October 28, 2026.
- Slack, Slack Enterprise Key Management. Checked October 28, 2026.
- Slack, Pricing plans. Checked October 28, 2026.
- Slack, Slack plans and features. Checked October 28, 2026.
- Slack, Set up SAML single sign-on for Slack. Checked October 28, 2026.
- Slack, Audit logs in Slack. Checked October 28, 2026.
- Slack, Export your workspace data. Checked October 28, 2026.