Rocket.Chat
A team chat platform with channels, direct messages, video calls and integrations that you can host yourself.
46.3k GitHub stars · Mixed or custom · last code push Oct 29, 2026 · GitHub · Website
Open-source and self-hosted alternatives to Slack
Team chat is one of the most mature open-source categories. These projects run in production at large organizations, and most offer a paid hosted plan if you do not want to run servers.
Category: Team chat · GitHub data as of Oct 29, 2026 · FAQ · Cost & self-hosting
Slack price change: Business+ $12.50 → $15 per user per month on annual billing, and $15 → $18 on monthly billing, with AI features bundled in. (effective Aug 17, 2025, details and sources)
| Project | What it is | License | GitHub stars | Last release | Runs as | Hosted plan |
|---|---|---|---|---|---|---|
| Rocket.Chat Active Mixed or custom | A team chat platform with channels, direct messages, video calls and integrations that you can host yourself. | Mixed or custom | 46.3k | Oct 28, 2026 | Self-hosted web app | Yes, from the project |
| Mattermost Active Mixed or custom | Mattermost is an open source platform for secure collaboration across the entire software development lifecycle. | Mixed or custom | 39.5k | Oct 28, 2026 | Self-hosted web app | Yes, from the project |
| Zulip Active Apache-2.0 | Zulip server and web application. Open-source team chat that helps teams stay productive and focused. | Apache-2.0 | 26.1k | Sep 21, 2026 | Self-hosted web app | Yes, from the project |
| Element Active AGPL-3.0 | Element, a chat app for the Matrix network, with end-to-end encrypted rooms and calls. | AGPL-3.0 | 13.6k | Oct 27, 2026 | Self-hosted web app | Yes, from the project |
Are they still maintained?
4 of 4 Slack alternatives here had a code push or release in the last 180 days (checked Oct 29, 2026).
- Rocket.Chat: active, last activity Oct 29, 2026 (0 days ago)
- Mattermost: active, last activity Oct 29, 2026 (0 days ago)
- Zulip: active, last activity Oct 29, 2026 (0 days ago)
- Element: active, last activity Oct 29, 2026 (0 days ago)
See every project in the "Is it still maintained?" tracker →
What switching from Slack costs
Slack: current plans and prices are on Slack's pricing page. Its most recent price change we track took effect on Aug 17, 2025 (see the price tracker).
| Alternative | How you run it | Software cost | What you pay for |
|---|---|---|---|
| Rocket.Chat | Your server, or the project's hosted plan | $0 (Mixed or custom, check terms) | A server you rent (or own), or the project's paid hosted plan. |
| Mattermost | Your server, or the project's hosted plan | $0 (Mixed or custom, check terms) | A server you rent (or own), or the project's paid hosted plan. |
| Zulip | Your server, or the project's hosted plan | $0 (Apache-2.0) | A server you rent (or own), or the project's paid hosted plan. |
| Element | Your server, or the project's hosted plan | $0 (AGPL-3.0) | A server you rent (or own), or the project's paid hosted plan. |
Self-hosting basics: Rocket.Chat, Mattermost, Zulip and Element need a server, which can be a small cloud server or a spare machine at home. For a sense of scale, DigitalOcean's price list shows a 1 GiB server at $6/month and 2 GiB at $12/month (checked Oct 29, 2026). Check each project's documented requirements before choosing a size, and budget time for updates and backups.
Don't want to run a server? Rocket.Chat, Mattermost, Zulip and Element offer a hosted plan run by the project itself. Prices change, so check each project's site.
License check: Rocket.Chat and Mattermost do not use a single standard open-source license that GitHub can detect. Read the license before using them in a business.
The options in more detail
Mattermost
Mattermost is an open source platform for secure collaboration across the entire software development lifecycle.
39.5k GitHub stars · Mixed or custom · last code push Oct 29, 2026 · GitHub · Website
Zulip
Zulip server and web application. Open-source team chat that helps teams stay productive and focused.
26.1k GitHub stars · Apache-2.0 · last code push Oct 29, 2026 · GitHub · Website
Element
Element, a chat app for the Matrix network, with end-to-end encrypted rooms and calls.
13.6k GitHub stars · AGPL-3.0 · last code push Oct 29, 2026 · GitHub · Website
Slack alternatives: common questions
What is the best open-source alternative to Slack?
It depends on how you use Slack. Of the 4 options here, Rocket.Chat is the most followed on GitHub (46.3k stars) and is actively maintained, with its latest release on Oct 28, 2026.
Is there a self-hosted Slack alternative?
Yes. Rocket.Chat, Mattermost, Zulip and Element run on a server you control, so your data stays with you. If you'd rather not run a server, Rocket.Chat, Mattermost, Zulip and Element also offer a hosted plan from the people who make them.
Is there a free alternative to Slack?
Yes. Every project on this page can be downloaded and used at no cost from its public repository. Server apps are free software, but you pay for the server they run on. Check the license of Rocket.Chat and Mattermost before using them in a business.
Are these Slack alternatives still maintained?
As of Oct 29, 2026, 4 of 4 had a code push or release in the last 180 days. None are flagged as inactive or archived. We re-check every project weekly.
How much does it cost to switch from Slack?
The software itself is free. For server apps, the main cost is hosting: as a reference point, DigitalOcean lists a 1 GiB server at $6/month and a 2 GiB server at $12/month (checked Oct 29, 2026). Check each project's documented requirements before choosing a size. The hidden cost is time: moving your data and, for self-hosted apps, keeping up with updates and backups.
Are all of these really open source?
Not all under a standard license. Rocket.Chat: GitHub could not identify a single standard license for this repository (often a mix of open-source and commercial parts). Read the LICENSE file before using it. Mattermost: GitHub could not identify a single standard license for this repository (often a mix of open-source and commercial parts). Read the LICENSE file before using it. The others use OSI-approved open-source licenses.
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