Open-source alternatives guide · Updated 2026
Compare the best free and open-source alternatives to Slack — 17 verified projects with explicit catalog relationships. Inspect licenses, GitHub activity, self-hosting signals, and migration fit before you switch.
Official product reference Slack↗Only explicit alternative relationships are shown—never inferred competitor claims.
This guide compares 17 verified open-source alternatives to Slack, including Rocket.Chat, Mattermost, NextCloud Server, and Huly.
Projects appear across Infrastructure, Content & Collaboration, and Business Software. 6 options include a self-hosting signal — see the self-hosted catalog. Ranking follows public GitHub stars and recorded momentum—not vendor marketing. Compare projects side by side, then confirm license fit, migration effort, and operational ownership before adopting any option.
Teams leaving Slack for Mattermost, Zulip, or Matrix-based stacks.
Migration tip: Pilot with one working group. Map channels, bots, and file storage before a company-wide cutover—integrations dominate migration cost.
Strongest repository-activity signal: Rocket.Chat · Jump to ranking · 45.8K stars
Slack is the default team chat for many companies. Open alternatives prioritize self-hosted messaging, Matrix federation, and clearer data residency.
Visit SlackCompare capabilities, licensing, and ownership model. Stars help with discovery; they are not a security or product-fit guarantee.
The Secure CommsOS™ for mission-critical operations
The Secure CommsOS™ for mission-critical operations Review the official repository, license, release activity, and deployment documentation before production adoption.
Mattermost is an open source platform for secure collaboration across the entire software development lifecycle..
Mattermost is an open source platform for secure collaboration across the entire software development lifecycle.. Review the official repository, license, release activity, and dep
A safe home for all your data
NextCloud is an open source software for synchronisation and file sharing for everyone, by users using the server NextCloud free of charge in the privacy of your home, to large com
Open-source alternative to Slack
Huly — All-in-One Project Management Platform (alternative to Linear, Jira, Slack, Notion, Motion)
Huly — All-in-One Project Management Platform (alternative to Linear, Jira, Slack, Notion, Motion) Review the official repository, license, release activity, and deployment documen
A glossy Matrix collaboration client for the web.
A glossy Matrix collaboration client for the web. Review the official repository, license, release activity, and deployment documentation before production adoption.
A free and open source instant messaging and VoIP chat app built for friends, groups, and communities.
A free and open source instant messaging and VoIP chat app built for friends, groups, and communities. Review the official repository, license, release activity, and deployment doc
Open-source alternative to Slack
Open-source and local-first Slack and Notion alternative that puts you in control of your data
Open-source and local-first Slack and Notion alternative that puts you in control of your data Review the official repository, license, release activity, and deployment documentati
Open-source alternative to Slack
Super simple group chat, without a subscription
Super simple group chat, without a subscription Review the official repository, license, release activity, and deployment documentation before production adoption.
Open-source alternative to Slack
Yet another matrix client
Yet another matrix client Review the official repository, license, release activity, and deployment documentation before production adoption.
The software powering Stoat
The software powering Stoat Review the official repository, license, release activity, and deployment documentation before production adoption.
Open-source alternative to Slack
A private, p2p alternative to Slack and Discord built on Tor & IPFS
A private, p2p alternative to Slack and Discord built on Tor & IPFS Review the official repository, license, release activity, and deployment documentation before production adopti
Open-source alternative to Slack
:wavy_dash: Overview of the open source code for Wire
:wavy_dash: Overview of the open source code for Wire Review the official repository, license, release activity, and deployment documentation before production adoption.
Open-source alternative to Slack
Mezon is a new way to communicate with your team. It's faster, better organized, better for WFH.
Mezon is a new way to communicate with your team. It's faster, better organized, better for WFH. Review the official repository, license, release activity, and deployment documenta
Open-source alternative to Slack
Privacy-first self-hosted team chat with channels, SSO options, and voice/video via LiveKit in a compact Go binary.
Chatto is a 2026 open-source Slack/Discord-style chat you can self-host as a single binary (or Docker Compose with NATS and LiveKit). Pilot moderation, mobile notifications, and vo
Open-source alternative to Slack
Valour is bringing communities into the future with unique features, blazing performance, and respect for users.
Valour is bringing communities into the future with unique features, blazing performance, and respect for users. Review the official repository, license, release activity, and depl
Open-source alternative to Slack
A multi-platform (Flutter) application for connecting to Matrix - an open network for secure, decentralized communication, with your favorite devices.
A multi-platform (Flutter) application for connecting to Matrix - an open network for secure, decentralized communication, with your favorite devices. Review the official repositor
Open-source alternative to Slack
SAMA - Simple but Advanced Messaging Alternative chat server, powered by uWebsockets.js
SAMA - Simple but Advanced Messaging Alternative chat server, powered by uWebsockets.js Review the official repository, license, release activity, and deployment documentation befo
Map must-have capabilitiesList the workflows in Slack you cannot drop during migration.
Verify the licenseConfirm it fits your use, distribution, and compliance model. Browse license briefs.
Run a proof of conceptTest real data, integrations, clients, and failure modes. Use Compare for side-by-side checks.
Plan ownershipAssess upgrades, backups, support, and an exit path. Read when self-hosting is worth it.
Mattermost, Zulip, and Matrix/Element cover most team chat needs. Choose based on threading model, SSO, and federation requirements.
Narrow the same alternatives by search, license, tags, or self-hosting signals when you need a tighter shortlist.
BrazilLicense not declaredThe Secure CommsOS™ for mission-critical operations
InfrastructureOpen-source projects grouped in this category for discovery and comparison.#
TypeScriptProjects tagged with this topic in the verified catalog.
Github ActionsProjects tagged with this topic in the verified catalog.
JavaScriptProjects tagged with this topic in the verified catalog.
SlackProprietary team messaging and collaboration platform.
United StatesLicense not declaredMattermost is an open source platform for secure collaboration across the entire software development lifecycle..
InfrastructureOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.SlackProprietary team messaging and collaboration platform.
GermanyAGPL-3.0-onlyA safe home for all your data
Content & CollaborationOpen-source projects grouped in this category for discovery and comparison.#
PHPProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.
LinuxDocumented runtime or deployment platform for this open-source project.SlackProprietary team messaging and collaboration platform.Huly — All-in-One Project Management Platform (alternative to Linear, Jira, Slack, Notion, Motion)
Business SoftwareOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.SlackProprietary team messaging and collaboration platform.
United KingdomAGPL-3.0A glossy Matrix collaboration client for the web.
InfrastructureOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.SlackProprietary team messaging and collaboration platform.A free and open source instant messaging and VoIP chat app built for friends, groups, and communities.
InfrastructureOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.SlackProprietary team messaging and collaboration platform.Open-source and local-first Slack and Notion alternative that puts you in control of your data
ProductivityOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.Self-hostedThis project carries a self-hosting or local-deployment signal. Verify the official install guide before production use.SlackProprietary team messaging and collaboration platform.Super simple group chat, without a subscription
Data & AnalyticsOpen-source projects grouped in this category for discovery and comparison.#
RubyProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.Self-hostedThis project carries a self-hosting or local-deployment signal. Verify the official install guide before production use.SlackProprietary team messaging and collaboration platform.Yet another matrix client
InfrastructureOpen-source projects grouped in this category for discovery and comparison.#TypeScriptProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.SlackProprietary team messaging and collaboration platform.United KingdomLicense not declaredThe software powering Stoat
Data & AnalyticsOpen-source projects grouped in this category for discovery and comparison.#
RustProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.
BashProjects tagged with this topic in the verified catalog.Self-hostedThis project carries a self-hosting or local-deployment signal. Verify the official install guide before production use.SlackProprietary team messaging and collaboration platform.A private, p2p alternative to Slack and Discord built on Tor & IPFS
Security & PrivacyOpen-source projects grouped in this category for discovery and comparison.#
CProjects tagged with this topic in the verified catalog.Github ActionsProjects tagged with this topic in the verified catalog.JavaScriptProjects tagged with this topic in the verified catalog.Self-hostedThis project carries a self-hosting or local-deployment signal. Verify the official install guide before production use.SlackProprietary team messaging and collaboration platform.:wavy_dash: Overview of the open source code for Wire
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