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Mattermost vs Slack 2026: Cost, Features, Comparison

A Versus B

Slack wins for general teams valuing simplicity and 2,000+ integrations; Mattermost wins for cost-conscious enterprises and compliance-driven organizations seeking data sovereignty and unlimited users at marginal cost.

Mattermost

Open-source, self-hosted team communication platform with AGPL v3 licensing.

Enterprises prioritizing data control, compliance officers needing sovereignty, budget-conscious organizations with IT resources, and companies requiring custom modifications.

Score71%
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VS

Slack

Cloud-native SaaS messaging platform with 2.9M daily active users and extensive integrations.

Small to mid-market teams, organizations without IT infrastructure, companies needing extensive third-party integrations, and teams prioritizing out-of-box functionality over customization.

Score71%
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7 attributes7 differences14 pros/cons
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7Sources
17Data Points
Sources:osalfinder.com (opens in new tab)·top-mcps.com (opens in new tab)·slack.com (opens in new tab)·larksuite.com (opens in new tab)·secumeet.com (opens in new tab)·mattermost.com (opens in new tab)·github.com (opens in new tab)
TL;DRVoice-readyDepends on priorities wins

Slack wins for general teams valuing simplicity and 2,000+ integrations; Mattermost wins for cost-conscious enterprises and compliance-driven organizations seeking data sovereignty and unlimited users at marginal cost.

Deciding factor: Slack: ecosystem maturity and zero ops overhead; Mattermost: 50-60% cost savings and data control

Key fact: Based on 2026 pricing data, Mattermost self-hosted eliminates per-user costs entirely while Slack costs $12.50/user/month; Slack has 19.3x more daily active users (2.9M vs 0.15M estimated).

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Our Verdict

AI-assisted

Choose Mattermost if your organization prioritizes data sovereignty, cost control at scale, and compliance requirements—self-hosting provides unlimited users at marginal cost and full code transparency. Choose Slack if you value ecosystem maturity, integrations, and hands-off management with 2.9M daily active users and industry-standard support.

TIE — neck and neck

M

Choose Mattermost if

Enterprises prioritizing data control, compliance officers needing sovereignty, budget-conscious organizations with IT resources, and companies requiring custom modifications.

S

Choose Slack if

Small to mid-market teams, organizations without IT infrastructure, companies needing extensive third-party integrations, and teams prioritizing out-of-box functionality over customization.

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Key Differences at a Glance

  • Deployment Model:✓ Mattermost wins(Self-hosted open-source vs Cloud-only SaaS)
  • Cost Per User/Month (Standard Plan):✓ Mattermost wins(Free (self-hosted) or $10/user/month (managed) vs $12.50 (Pro plan, 2026))
  • Daily Active Users (2026):✓ Slack wins(2.9 million vs 150,000+ (estimated enterprise))
See all 7 differences

Key Facts & Figures

4 numeric metrics compared

MetricMattermostSlackRatio
Available Integrations(count)500+2,000+
Monthly Cost (100-person org, Pro tier)(USD)$1,000 (managed) or $0 (self-hosted)$1,250
Global Daily Active Users (2026)(millions)0.15 (estimated)2.9
Time to Deploy (typical setup)(days)7-30 (self-hosted, IT-dependent)0.25 (sign-up + invite)

Sourced from publicly available data ·

Key Differences

7 attributes compared head-to-head

M
5Mattermost
Mattermost leads
S
2Slack
  • Deployment Model

    Mattermost

    Self-hosted open-source(winner)

    Slack

    Cloud-only SaaS

  • Cost Per User/Month (Standard Plan)

    Mattermost

    Free (self-hosted) or $10/user/month (managed)(winner)

    Slack

    $12.50 (Pro plan, 2026)

  • Daily Active Users (2026)

    Mattermost

    150,000+ (estimated enterprise)

    Slack

    2.9 million(winner)

  • Message Search History

    Mattermost

    Unlimited (self-hosted)(winner)

    Slack

    3 months (free plan), unlimited (paid)

  • Source Code Access

    Mattermost

    Full open-source (AGPL v3)(winner)

    Slack

    Proprietary, no access

Full Comparison

MMattermost
SSlack
Source Code Access
Full (AGPL v3 open-source)
Proprietary, no access
Available Integrations(count)
500+
2,000+
Monthly Cost (100-person org, Pro tier)(USD)
$1,000 (managed) or $0 (self-hosted)
$1,250
Global Daily Active Users (2026)(millions)
0.15 (estimated)
2.9
Deployment Options
Self-hosted or managed cloud
Cloud-only (AWS regions)
Time to Deploy (typical setup)(days)
7-30 (self-hosted, IT-dependent)
0.25 (sign-up + invite)
SOC 2 Compliance
Self-achievable via self-hosting
Slack-provided certification

Pros & Cons

10 pros·4 cons across both

M
S
M

Mattermost

+5-2

Pros

Zero per-user licensing costs (self-hosted model) or $10/user/month (managed service)
Full source code access enables custom branding, security audits, and feature modifications
Unlimited message search history and user limits regardless of plan tier
Complete data residency control—host on own servers or private cloud infrastructure
GDPR/HIPAA/SOC 2 compliance achievable through self-hosting without vendor lock-in

Cons

Smaller integration ecosystem (500+ vs Slack's 2,000+) limits third-party tool connectivity
Requires IT infrastructure expertise and server maintenance responsibility
S

Slack

+5-2

Pros

2,000+ integrations in official marketplace including Salesforce, Jira, GitHub, and SAP
2.9 million daily active users (2026) creates largest ecosystem and third-party support
Zero infrastructure management—Slack maintains security, uptime, and scaling
Workflow Builder allows no-code automation without custom development
Mobile apps with full feature parity and reliable push notifications

Cons

$12.50/user/month Pro plan cost scales to $125,000+/year for 1,000-person org (vs Mattermost's marginal cost)
Message retention limited to 3 months on free plan; paid plans required for compliance archiving

Frequently Asked Questions

5 questions

  1. Mattermost offers 500+ integrations (community and official), compared to Slack's 2,000+. For popular tools (GitHub, Jira, Salesforce), Mattermost has parity, but niche third-party apps favor Slack. Mattermost's open-source model allows custom API integrations if needed.

  2. Yes. A 1,000-person org pays $10,000/month ($10/user) on Mattermost managed service vs. $12,500/month ($12.50/user) on Slack Pro. Self-hosted Mattermost has no per-user cost, reducing TCO further for IT-resourced teams.

  3. No. Slack is cloud-only, hosted on AWS with regional data centers (US, EU, Australia). Organizations requiring on-premise deployment must choose Mattermost or competitor solutions like Microsoft Teams.

  4. Mattermost's self-hosted model provides full data residency control and HIPAA/GDPR compliance without vendor lock-in. Slack offers BAA (HIPAA Business Associate Agreement) and GDPR compliance certification but stores data on AWS with limited regional options.

  5. Mattermost uses AGPL v3, which allows free commercial use and full code modification. AGPL requires sharing derivative code changes, but not modifications to Mattermost itself if deployed internally. Enterprise customers can purchase proprietary licenses to avoid AGPL obligations.

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