Secure, self-hosted team messaging platform as an alternative to Slack
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Mattermost can be used as an alternative to these commercial products.
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Mattermost is the best open source alternative to Slack in 2026. Self-hosted team chat, MIT license, no per-seat fees — replaces Slack Pro at $8.75/user/month.
Self-host Mattermost vs Slack in 2026: cost per seat, admin features, and migration steps compared. Mattermost saves $12/user/month for 20+ person teams.
Self-host Mattermost as a Slack alternative for teams in 2026. MIT license, ~30K stars — channels, threads, integrations, bots, slash commands for 2026.
SaaS to self-hosted, step-by-step — one PDF.
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