Mattermost Community Edition is an open‑source, self‑hosted Slack‑like chat platform for secure team collaboration. Looking for other free instant‑messaging solutions that can replace or complement Mattermost? Below is a curated list of 20 free (or free‑tier) alternatives.
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Open‑source, self‑hosted chat platform with real‑time messaging, video calls, and extensive integrations.
Threaded open‑source chat that combines real‑time and asynchronous messaging, ideal for large, active teams.
Secure, federated messenger built on the Matrix protocol; offers end‑to‑end encryption and bridge support.
Popular cloud‑based chat with searchable message history (up to 10k messages), integrations, and file sharing.
Voice, video, and text chat platform with server‑based channels; free tier includes unlimited messaging.
Collaboration hub offering chat, video meetings, and file collaboration with Office 365 integration.
Cloud‑based messenger with large group support, bots, and end‑to‑end encrypted secret chats.
Privacy‑focused messenger with strong end‑to‑end encryption for text, voice, and video calls.
Secure collaboration suite offering encrypted messaging, voice, and video calls for teams.
Encrypted chat built into the Keybase platform, with file sharing and team channels.
Open network for secure, decentralized communication; can be self‑hosted with custom UI.
Integrated chat and video call app for Nextcloud installations, supporting end‑to‑end encryption.
Team messaging app with channels, direct messages, and limited integrations at no cost.
Combines chat, task management, and workflow automation; free tier supports up to 6 users.
Free messaging solution for small businesses, offering quick replies, labels, and catalog features.