Element, Mattermost, and Rocket.Chat are all open-source, self-hostable Slack alternatives aimed at security-conscious and regulated organizations, but each…
Open Source / Freemium (free self-hosted Community edition plus paid Enterprise and Sovereign tiers) · From Free (self-hosted Community edition); Enterprise and Sovereign pricing available on request
Best for: Organizations that need federated, end-to-end encrypted chat with sovereign or air-gapped deployment options for government and defense use cases
Freemium (free self-hosted Community edition, plus paid Pro and Enterprise plans) · From Free (Community); Pro from $8/user/month billed annually
Best for: Organizations that want to combine internal team chat with customer-facing omnichannel support in one self-hosted platform
At a Glance
Element
Mattermost
Rocket.Chat
Primary category
Team Chat
Team Chat
Team Chat
Rating
Not documented
Not documented
Not documented
Pricing model
Open Source / Freemium (free self-hosted Community edition plus paid Enterprise and Sovereign tiers)
Freemium
Freemium (free self-hosted Community edition, plus paid Pro and Enterprise plans)
Starting price
Free (self-hosted Community edition); Enterprise and Sovereign pricing available on request
Free (Starter, self-hosted); Professional from $10/user/month
Free (Community); Pro from $8/user/month billed annually
Free plan
Yes
Yes
Yes
Free trial
Not documented
Not documented
Not documented
Platforms
Web, iOS, Android, Mac, Windows
Web, iOS, Android, Mac, Windows
Web, iOS, Android, Mac, Windows
Team collaboration
Not documented
Not documented
Not documented
AI features
Not documented
Not documented
Not documented
Public API
Yes
Not documented
Yes
Standout Differences
Shared open-source, self-hosted foundation
Element, Mattermost, and Rocket.Chat are all open source and offer free self-hosted tiers, giving regulated organizations control over data residency that closed SaaS platforms cannot match.
Element, Mattermost, Rocket.Chat
Matrix federation and decentralization
Element's Matrix protocol allows independently run servers to communicate with each other, a decentralized architecture neither Mattermost nor Rocket.Chat's core chat product replicates.
Element
Built-in workflow automation
Mattermost's Playbooks feature provides checklist-driven workflow automation for incident response and DevOps processes that is not native to Slack or the other two tools compared here.
Mattermost
Omnichannel customer support bundled in
Rocket.Chat combines internal team messaging with customer-facing omnichannel support channels in a single platform, a use case Element and Mattermost do not target.
Rocket.Chat
Government and defense-grade deployments
All three tools have documented traction in regulated, government, or defense environments, though Element and Rocket.Chat explicitly market government and defense-grade deployment options.
Element, Rocket.Chat
Feature-by-Feature
Deployment and Architecture
Feature
Element
Mattermost
Rocket.Chat
Self-hosted deployment
Available
Available
Available
Federated, decentralized architecture
Available
Unavailable
Available
Security
Feature
Element
Mattermost
Rocket.Chat
End-to-end encryption
Available
Not documented
Available
Air-gapped or sovereign-grade deployment
Available
Available
Available
Workflow and Support
Feature
Element
Mattermost
Rocket.Chat
Built-in workflow automation (playbooks or checklists)
Unavailable
Available
Not documented
Omnichannel customer-facing support
Unavailable
Unavailable
Available
Pricing
Feature
Element
Mattermost
Rocket.Chat
Free self-hosted tier
Available
Available
Available
Pricing Compared
Starting price reflects the lowest paid tier, not the full cost for every team size or usage level.
Element
Community — Free n/a
Enterprise — Custom (per seat/month) monthly
Sovereign — Custom (per deployment) custom
Mattermost
Starter — Free N/A
Professional — $10/user/month annual
Enterprise — Custom annual
Rocket.Chat
Community — Free N/A
Pro — $8/user/month annual
Enterprise / Government / Defense — Custom custom
Pros & Cons
Element
Pros
Fully open source under the AGPL with no artificial caps on users, messages, or core features, even on the free self-hosted tier.
Decentralized, federated architecture gives organizations full control over data residency, unlike single-vendor centralized platforms.
End-to-end encryption is enabled by default in private rooms, backed by a well-regarded cryptographic protocol design.
Strong track record with government and defense customers, including deployments in France and Germany, validating its security posture.
Cons
Self-hosting a Synapse homeserver requires meaningful technical expertise and ongoing infrastructure maintenance.
Enterprise and Sovereign tier pricing is not published and requires contacting sales, complicating budget comparisons against competitors.
The federated architecture and richer feature set can feel more complex than simpler, purely consumer-focused apps like Signal.
Some advanced enterprise features, such as SLAs and directory integration, are reserved for paid tiers rather than the free Community edition.
Mattermost
Pros
Fully open-source core with self-hosted and air-gapped deployment options
Strong fit for regulated industries, government and defense customers
Playbooks provide built-in workflow automation not native to Slack
Deep integrations with developer and DevOps tooling
Lightweight architecture (single Go binary) makes self-hosting comparatively simple
Cons
Smaller app/integration marketplace than Slack or Microsoft Teams
Enterprise pricing is custom-quoted and not publicly transparent
Self-hosting requires ongoing server maintenance and updates
UI and mobile experience is generally considered less polished than Slack
Annual prepaid billing only for official Professional and Enterprise licenses, no monthly option
Rocket.Chat
Pros
Free, self-hosted Community edition with no user-count-based licensing cost beyond infrastructure
Full source code access supports auditing and customization
Flexible deployment options including air-gapped and sovereign cloud for regulated industries
Combines internal team chat and customer-facing omnichannel support in one platform
Cons
Self-hosting requires infrastructure management and technical expertise the hosted competitors don't demand
Enterprise, Government, and Defense pricing is not published and requires a sales conversation
Community edition caps out at fifty users before requiring a paid plan
UI and performance can lag behind polished proprietary competitors like Slack for casual users
Use Cases
Choose Element: Organizations that need federated, end-to-end encrypted chat with sovereign or air-gapped deployment options for government and defense use cases
Choose Mattermost: Regulated and technical organizations that want a Slack-like self-hosted platform with built-in workflow automation and DevOps integrations
Choose Rocket.Chat: Organizations that want to combine internal team chat with customer-facing omnichannel support in one self-hosted platform
Element
Self-Hosted Team Chat — Organizations run their own Synapse homeserver to replace Slack or Teams with a fully self-controlled, encrypted messaging platform.
Sovereign Government Communications — Government agencies and defense organizations deploy Element's Sovereign tier for air-gapped, high-security internal messaging.
Cross-Organization Federated Messaging — Businesses and communities use Matrix's federation to communicate across independently hosted servers without relying on a single vendor.
Mattermost
Incident response and DevOps workflows — Engineering teams use Playbooks to coordinate incident response with automated checklists and dedicated channels.
Regulated and government communication — Public-sector and financial-services organizations need self-hosted or air-gapped messaging to meet compliance requirements.
Secure internal team chat — Organizations that want Slack-like messaging while keeping full control of where data is stored.
Rocket.Chat
Privacy-focused team messaging — Organizations that need to keep chat data within their own infrastructure self-host Rocket.Chat's Community edition.
Regulated government and defense communication — Public-sector and defense organizations use Rocket.Chat's air-gapped and sovereign cloud deployment options for secure communication.
Combined internal and customer chat — Businesses use Rocket.Chat for both internal team collaboration and customer-facing omnichannel support in a single platform.
Frequently Asked Questions
Which of these tools is best for DevOps teams that want built-in workflow automation?
Mattermost, thanks to its Playbooks feature for checklist-driven incident response and workflow automation.
Which tool combines internal chat with customer-facing support?
Rocket.Chat, which bundles omnichannel customer service alongside standard team messaging.
Which tool uses a federated protocol that lets independently run servers talk to each other?
Element, built on the Matrix protocol, though Rocket.Chat also lists federation support as a feature.
Do all three support air-gapped or government-grade deployments?
Yes, all three offer deployment options aimed at regulated, government, or defense environments, though the exact certifications and pricing require contacting sales.
Is there a free self-hosted option for each tool?
Yes. Element's Community tier, Mattermost's Starter tier, and Rocket.Chat's Community edition are all free to self-host, though Rocket.Chat's free tier caps out at fifty users.
Which tools document end-to-end encryption as a feature?
Element and Rocket.Chat both list end-to-end encryption; Mattermost does not document it as a core feature in the data reviewed here.