9 Best Slack Alternatives & Competitors (2026)

Slack is a cloud-native team messaging platform popular for everyday business communication. Its strengths include polished UX, extensive app marketplace, and fast search across conversations. Compared to Mattermost, Slack offers easier setup but lacks native on-premise deployment and the same level of data sovereignty required by defense or critical infrastructure teams. Pricing follows a freemium model with paid tiers for advanced administration.

Microsoft Teams combines chat, video, and deep integration with Microsoft 365. It excels in large enterprises already using Office tools and provides strong compliance certifications. Unlike Mattermost's self-hosted focus, Teams is primarily SaaS with limited on-premise options, making it less suitable for air-gapped or highly sovereign use cases where full infrastructure control is mandatory.

Rocket.Chat is an open-source team chat platform that supports self-hosting and omnichannel features. It provides similar channel and integration capabilities to Mattermost with strong emphasis on customization. While both are freemium, Rocket.Chat sometimes trades depth in mission-critical playbooks and defense-specific security modules for broader omnichannel support.

Zulip offers threaded conversations that help organize complex technical discussions. It is open source and can be self-hosted. Compared with Mattermost, Zulip provides superior threading but fewer native playbook and incident response tools, making it better for developer teams than for security operations centers needing structured workflows.

Element is a Matrix-based secure messenger focused on end-to-end encryption and federation. It supports self-hosting and is popular in privacy-conscious and government circles. While Element matches Mattermost's sovereignty emphasis, it is more messaging-centric and offers fewer built-in DevSecOps or playbook automation features.

Wire focuses on secure enterprise messaging with end-to-end encryption and on-premise options. It appeals to regulated industries needing compliance. Compared to Mattermost, Wire provides strong privacy defaults but offers less emphasis on integrated playbooks and real-time DevSecOps tooling.

Cisco Webex combines messaging with enterprise-grade video and calling. It targets large organizations needing compliance and security certifications. Compared to Mattermost, Webex is stronger in video but weaker in flexible self-hosted deployment and deep open-source extensibility for custom mission workflows.

Discord provides voice, video, and text channels with strong community features. It is easy to deploy but cloud-only and consumer-oriented. For teams leaving Mattermost, Discord lacks enterprise compliance, audit controls, and self-hosting options required in regulated industries.