team-chat
(3)
Rocket.Chat
Bring together messaging, voice, video, critical apps, and AI to keep teams connected and missions protected.
Mattermost
Mattermost is an open-source, self-hostable collaboration platform built for organizations that cannot put their conversations in someone else's cloud. Started as a game studio's internal chat tool and open-sourced in 2015, it grew into the leading self-hosted alternative to Slack and Microsoft Teams, combining channel messaging, voice and screen sharing, incident-response Playbooks, and integrated AI agents. Its customers skew toward defense, government, financial services, and technology organizations - from the U.S. Air Force to Uber - that need data sovereignty, air-gapped deployment, and government-grade security.
Swit
Swit is an AI-powered enterprise Work OS that fuses team chat, task management, project workflows and integrations into a single hub. Founded by Josh Lee and Max Lim in 2017, it serves more than 40,000 teams across 184 countries and is headquartered in San Francisco with roots in Seoul.