Slack vs Mattermost: Which is Better in 2026?
Choosing between Slack and Mattermost comes down to understanding what each tool does best. This comparison breaks down the key differences so you can make an informed decision based on your specific needs, not marketing claims.
Bottom line: Slack is our overall Internal Comms pick. Pick Mattermost if you need a free tier to start with.
Short on time? Here's the quick answer
Based on published vendor pricing and features and on public review data, here's who should pick what:
Slack
Central hub for workplace communication and collaboration
Best for you if:
- • You want intuitive interface with low learning curve, most teams adopt it within days
Mattermost
Open-source team collaboration platform
Best for you if:
- • You want open source Slack alternative
| At a Glance | Slack | Mattermost |
|---|---|---|
Starts at | Free Free plan | Free Free plan |
Category | Communication Productivity | Communication Team Chat |
Rating | 4.2/5 G2 4.5 · Capterra 4.7 · TrustRadius 4.5 64,990 reviews | 4.3/5 G2 4.3 · Capterra 4.4 · SourceForge 4.3 604 reviews |
Free plan | Yes | Yes |
Watch out for | 90-day message history on Free: after 90 days, old messages become invisible (not deleted, they return if you upgrade). This is the most common upgrade trigger and feels coercive for teams that relied on older unlimited history | n/a |
Choose Slack or Mattermost?
Choose Slack if
- You want intuitive interface with low learning curve, most teams adopt it within days
- You want deepest third-party integration ecosystem of any team chat tool (2,600+ apps)
- Budget matters (Free vs Free)
Choose Mattermost if
- You want open source Slack alternative
- You want self-hostable
In-Depth Analysis
Slack
Central hub for workplace communication and collaboration
Slack is the default team messaging tool, and its pricing reflects that dominance.
Watch out
90-day message history on Free: after 90 days, old messages become invisible (not deleted, they return if you upgrade). This is the most common upgrade trigger and feels coercive for teams that relied on older unlimited history
Strengths
- Pro: Intuitive interface with low learning curve, most teams adopt it within days
- Pro: Deepest third-party integration ecosystem of any team chat tool (2,600+ apps)
- Pro: Slack Connect eliminates email chains with external partners via shared channels
- Pro: Powerful search across all messages, files, and connected apps from one bar
- Pro: Workflow Builder lets non-technical users automate routine processes
Weaknesses
- Con: Free plan limits message history and allows only a limited number of app integrations
- Con: Notification overload in large workspaces, channels can become noisy without discipline
- Con: Pricing adds up quickly for large teams
- Con: No built-in project management, still requires separate tools like Asana or Jira
- Con: Slack AI features require higher-tier plans, not available on all plans
Key features
Mattermost
Open-source team collaboration platform
Mattermost's pricing is fair, offering a generous Free tier for small teams.
Strengths
- Pro: Open source Slack alternative
- Pro: Self-hostable
- Pro: Good for compliance
- Pro: No per-user cloud cost
- Pro: Customizable
Weaknesses
- Con: Less polished than Slack
- Con: Smaller integration library
- Con: Self-hosting required for best value
- Con: Learning curve
- Con: Community smaller
Key features
Pricing: Slack vs Mattermost
| Plan | Slack | Mattermost |
|---|---|---|
| Tier 1 | Free Free | Free Free |
| Tier 2 | $7.25 /user/month (annual) Pro | $10 Professional |
| Tier 3 | $15 /user/month (annual) Business+ | Custom Enterprise |
| Tier 4 | custom Enterprise+ | N/A |
Pricing verified from each vendor's public pricing page. Compare in detail on Slack pricing and Mattermost pricing.
Key Takeaways
Slack
- Larger review base (64,990 reviews)
- Free tier available
- Our pick for this comparison
Mattermost
- Higher user rating: 4.3/5 vs 4.2/5
The Bottom Line
Slack is our overall Internal Comms pick.
Frequently Asked Questions
Is Slack or Mattermost better in 2026?
Slack is our overall Internal Comms pick. Pick Slack for communication workflows (main strength: intuitive interface with low learning curve, most teams adopt it within days). Pick Mattermost for communication workflows (main strength: open source Slack alternative).
What are Slack and Mattermost used for?
Slack: Central hub for workplace communication and collaboration. Mattermost: Open-source team collaboration platform.
What does Slack cost vs Mattermost?
Slack's paid plans start at Free (Pro). Mattermost's paid plans start at Free (Professional).
What's the main difference between Slack and Mattermost?
Slack's main strength: intuitive interface with low learning curve, most teams adopt it within days. Mattermost's main strength: open source Slack alternative.