Free & open source alternatives to Slack

4 free team chat apps to use instead of Slack by Salesforce

The best free alternative to Slack is Mattermost. Channels, threads, voice calls and bots, with all data on your company's server and no 90-day history cap.

Other great options: Rocket.Chat, Zulip and Element.

Quick pick: Slack-like and self-hosted: Mattermost. Also need live chat with website visitors: Rocket.Chat. Large teams with topic-based threads: Zulip.

Reviewed November 2026 against each vendor's official website.

Official ways to use Slack for free

Slack Free plan only lets you see messages and files from the last 90 days.

Free plans and trial lengths are set by the vendor and can change. Check the official website before signing up.

4 best alternatives to Slack

Mattermost

Notes & teamwork HealthGood (95/100)39,557

Open sourceTechnical setup

Channels, threads, voice calls and bots, with all data on your company's server and no 90-day history cap.

Open-source, self-hosted Slack alternative with channels, direct messages, threads, voice calls and bots.

Slack-like, with data on your company's servers
Mobile apps

Platforms: Self-hosted · Windows · Mac · Linux · Android · iPhone · Web

Mattermost details Official website ↗

Rocket.Chat

Notes & teamwork HealthGood (85/100)46,375

Open sourceTechnical setup

Internal team chat plus live chat with customers.

Open-source team chat platform that also handles customer support. Includes website live chat and an omnichannel inbox.

Internal chat and customer chat in one tool
Self-hosted with many integrations

Platforms: Self-hosted · Web · Windows · Mac · Linux · Android · iPhone

Rocket.Chat details Official website ↗

Zulip

Notes & teamwork HealthGood (90/100)26,190

Open sourceSome learning curve

Topic-based threads so conversations don't get buried.

Open-source team chat that organizes messages by topic, so conversations don't get buried like in Slack. Good for large or distributed teams.

Topic-based threads are easy to catch up on
Self-hosted edition is free and full-featured

Platforms: Web · Windows · Mac · Linux · Android · iPhone · Self-hosted

Zulip details Official website ↗

Element

Notes & teamwork HealthGood (85/100)13,640

Open sourceSome learning curve

End-to-end encrypted chat on the Matrix network.

Open-source, end-to-end encrypted chat app built on the Matrix protocol. Used by several European government agencies.

End-to-end encrypted and decentralized
Can be self-hosted

Platforms: Web · Windows · Mac · Linux · Android · iPhone · Self-hosted

Element details Official website ↗

Quick comparison

App	Type	Platforms	Ease of use	GitHub stars
Mattermost	Open source	Self-hosted, Windows, Mac, Linux, Android, iPhone, Web	Technical setup	39,557
Rocket.Chat	Open source	Self-hosted, Web, Windows, Mac, Linux, Android, iPhone	Technical setup	46,375
Zulip	Open source	Web, Windows, Mac, Linux, Android, iPhone, Self-hosted	Some learning curve	26,190
Element	Open source	Web, Windows, Mac, Linux, Android, iPhone, Self-hosted	Some learning curve	13,640

Open source: anyone can use, study and modify it, including businesses. Free: no cost, but the code is closed. Freemium: a lasting free plan with paid tiers for extra features. Source available: code is public but the license adds conditions.

FAQ

What is the best free alternative to Slack?

The most popular picks are Mattermost, Rocket.Chat, Zulip and Element. Slack-like and self-hosted: Mattermost. Also need live chat with website visitors: Rocket.Chat. Large teams with topic-based threads: Zulip.