Best Slack Alternatives (2026)
Open-source, self-hostable, and lower-cost alternatives to Slack — ranked and compared.
Why teams look beyond Slack
Slack's dominance in team messaging comes with a pricing model that punishes growth. At $7.25 per user per month on the Pro plan, a 50-person team spends over $4,300 annually just to retain full message history — because the free tier caps search at 90 days and 10,000 messages, which a moderately active team exhausts in weeks. Every new hire, contractor, and external collaborator added through Slack Connect is another line item that compounds each billing cycle.
For teams in regulated industries or jurisdictions with strict data residency requirements, the pricing question is secondary. Slack is a fully closed, cloud-hosted service owned by Salesforce, with no self-hosting option. That means respondent data, file attachments, and conversation history flow through Salesforce's infrastructure. HIPAA Business Associate Agreements, FedRAMP authorization, and air-gapped deployments are either unavailable or restricted to the highest enterprise tiers at negotiated contract pricing.
The open-source self-hostable messaging tools in this directory — Mattermost and Rocket.Chat in particular — cover the Slack use case with no per-seat billing on self-hosted deployments and full control over where the data sits. The trade-off is operational overhead: you provision the server, manage upgrades, and own the uptime SLA. For teams with the engineering capacity to run their own services, that trade-off is straightforward.
The 2 best Slack alternatives
Open-source team chat and omnichannel customer messaging platform.
- MIT license with a large feature set available for free on self-hosted installs
- Omnichannel capabilities blend internal chat and external customer communications
- JavaScript/Meteor stack can be resource-intensive compared to lighter alternatives
Open-source, self-hosted team messaging built for security-conscious and DevOps teams.
- Full data sovereignty — runs on your own servers with no vendor access
- MIT-licensed core is free to self-host with no seat caps
- UI and mobile experience lag behind Slack's polish
Slack alternatives compared
| Spec | Rocket.Chat | Mattermost |
|---|---|---|
| License | MIT | MIT / Open-core |
| Open source | ✓ | ✓ |
| Self-host | ✓ | ✓ |
| Starting price | Free / self-host | Free / self-host |
| Stars | 42,000 | 32,000 |
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Frequently asked questions
What is the best Slack alternative?
Rocket.Chat is our top pick — Open-source team chat and omnichannel customer messaging platform. It is open source and self-hostable, Free / self-host.
Is there a free or open-source Slack alternative?
Yes. Rocket.Chat, Mattermost are open source, and most can be self-hosted for free aside from infrastructure cost.
Can I self-host an alternative to Slack?
Yes — Rocket.Chat, Mattermost support self-hosting, giving you full data ownership.