GitPop
4 candidates

Open source alternatives to Slack

Cloud-based team chat with channels, threads, integrations, and voice huddles. · Salesforce

Pricing: Free up to 90 days of message history; paid plans from $7.25/user/mo

Slack is the default for team chat in most tech companies in 2026. Open-source alternatives split into two camps: self-hostable Slack-replacements (Mattermost, Rocket.Chat) for teams that need data residency, and protocol-based clients (Element) for teams that want interoperability with Matrix. The choice depends on whether you want a 'Slack but self-hosted' (Mattermost) or a 'different protocol entirely' (Element) experience.

The 4 candidates, ranked by PopScore

  1. #01mattermost/mattermost

    Self-hostable Slack replacement with channels, threads, and integrations. The closest 'Slack but on your server' option.

    GitHub
  2. #02RocketChat/Rocket.Chat

    Mature open-source team chat with omnichannel support (WhatsApp, SMS, email) — picks up where Slack leaves off for customer-support use cases.

    GitHub
  3. #03element-hq/element-web

    Matrix protocol client with end-to-end encryption. The right pick if you want protocol-level interoperability (bridge to Slack, Discord, etc.) and a security-first posture.

    GitHub
  4. #04zedeus/nitter

    Privacy-respecting Twitter frontend. Not a Slack alternative, but a useful complementary open-source tool in the same 'social' space.

    GitHub

Related alternatives

Looking for a side-by-side comparison of two open-source projects? The compare matrix has 60+ "X vs Y" pages. Looking for a curated "best of" list for a specific category? See Best AI tools 2026 (and the 7 other category editions).

Best open source alternatives to Slack (2026) · GitPop