Alternatives · 2026
6 self-hosted Slack alternatives for your own servers.
Sometimes "where does our data live?" is not a preference but a requirement — a regulator, a client contract, or a security team that wants the US CLOUD Act out of scope. Slack has no answer to that: there is no self-hosted Slack, and there never has been.
The good news is that the self-hosted field has matured. This guide compares six tools you can genuinely run on your own servers — one of them ours, labelled as such — with the operational cost stated as plainly as the benefits.
Five questions for a self-hosted shortlist.
- (01)
Is self-hosting the real product?
First-class deployment path with documentation and support — or a community edition kept at arm's length?
- (02)
Can it run air-gapped?
Fully offline networks are the hardest test: no callbacks, no license pings, no CDN dependencies.
- (03)
What is the day-two ops burden?
Upgrades, backups, monitoring. A chat server you dread upgrading is a liability, not an asset.
- (04)
How much beyond chat do you get?
Every extra tool you self-host is another service to patch. Coverage per deployment matters double here.
- (05)
How is it licensed?
Open source, open core or commercial — what matters is knowing which features sit where before you commit.
The six contenders.
- 01(01)
Polybase
Our productOne self-hosted workspace, not one self-hosted chat
Full disclosure: Polybase is our product. Read this entry as the maker's perspective — the caveat below is as real as everyone else's.
Polybase self-hosts an entire workspace — chat, calls, tasks, docs, email, tables and automation — from a single Docker Compose deployment, single tenant per instance. It runs fully offline in air-gapped networks; calls use a self-hosted LiveKit server. Backups are portable and SQLite-based, with uploaded files living on the filesystem and covered by your standard volume snapshots.
- Best for
- Organisations that want to self-host one workspace instead of a chat server plus four more services.
- Hosting model
- Self-hosted / air-gapped via Docker Compose; EU cloud and private VPC also offered.
- Honest caveat
- Not open source, and a young product: SOC 2 / ISO 27001 and SSO/SAML are roadmap items.
- 02(02)
Mattermost
The DevOps default for self-hosted chat
Mattermost is the name most engineering teams reach for first: open-core, deployable via Docker or Kubernetes, with strong incident and playbook workflows. Its documentation and operational tooling reflect years of production self-hosting.
- Best for
- DevOps and platform teams that want a proven, well-documented self-hosted chat server.
- Hosting model
- Self-hosted (Docker/Kubernetes); vendor cloud also available.
- Honest caveat
- It self-hosts chat, not your whole stack — docs, boards and email remain separate services — and several enterprise features are paid.
- 03(03)
Rocket.Chat
Open-source chat with a public-sector track record
Rocket.Chat has been self-hosted in government, defence and regulated industries for years, and adds omnichannel customer messaging to the same deployment. The open-source core is genuinely capable on its own.
- Best for
- Public-sector and regulated organisations with formal deployment requirements.
- Hosting model
- Self-hosted or Rocket.Chat's hosted cloud.
- Honest caveat
- The admin surface is large, and a number of advanced capabilities are reserved for paid plans.
- 04(04)
Element (Matrix)
Run your own node of an open network
Self-hosting Matrix means running a homeserver such as Synapse and joining a federated, end-to-end encrypted network — the most radical answer to vendor dependence on this list. Element provides the polished client on top.
- Best for
- Organisations that want federation and E2EE, and have the ops maturity to run a homeserver.
- Hosting model
- Self-hosted homeserver or managed hosting from Element.
- Honest caveat
- The heaviest ops lift here: homeserver tuning, federation quirks and an admin experience that trails centralised tools.
- 05(05)
Zulip
Self-hosted chat your future self can read
Zulip's topic-based threading keeps high-volume channels readable years later, and its self-hosted edition is a first-class citizen with a well-maintained installer and upgrade path. Distributed teams and open-source communities run it at serious scale.
- Best for
- Async-heavy teams that want self-hosted chat with genuinely readable history.
- Hosting model
- Self-hosted or Zulip Cloud.
- Honest caveat
- The topic model asks for discipline, and beyond chat you still self-host everything else separately.
- 06(06)
Nextcloud Talk
Chat and calls inside the Nextcloud platform
Nextcloud Talk adds chat and calls to the open-source Nextcloud file platform, which is widely deployed across European public administration and education. If you already run Nextcloud, Talk is one app-install away.
- Best for
- Organisations already invested in Nextcloud for files and groupware.
- Hosting model
- Self-hosted (or hosting via Nextcloud providers).
- Honest caveat
- Chat and calls are companions to the file platform rather than its core — dedicated chat tools go deeper on chat, and larger call setups need extra components.
Where Polybase wins — and where we don't win yet.
You are reading this list on our site, so here is the part vendors usually skip.
- One deployment, whole workspaceChat, calls, tasks, docs, email, tables and automation in a single Docker Compose deployment — one service to patch instead of five.
- A real air-gap storyPolybase runs fully offline; calls use a self-hosted LiveKit server. No callbacks, no license pings.
- Sovereignty by architectureYour servers, your keys, single tenant per instance. The US CLOUD Act's reach ends where your infrastructure begins.
- Boring, portable backupsPortable, SQLite-based database backups; uploaded files live on the filesystem and are covered by your standard volume snapshots.
- AI that stays insideBring your own model — including self-hosted via Ollama or LocalAI — so even the assistant can stay on your infrastructure.
- Not open sourcePolybase is commercial software you can self-host. If open-source licensing is a hard requirement, Mattermost, Rocket.Chat, Zulip, Element and Nextcloud are the list.
- CertificationsNot certified yet — SOC 2 and ISO 27001 are on our roadmap. We answer security questionnaires and architecture questions today.
- Enterprise sign-onSSO/SAML/SCIM are on the roadmap; today sign-in is email/password and magic links.
- Ecosystem and appsThere is no app marketplace or guided importer. Polybase is available on desktop, mobile, web and as an installable PWA.
Self-hosting your team chat.
Yes. Polybase deploys offline via Docker Compose and runs fully offline; calls use a self-hosted LiveKit server inside the same network.
No — Polybase is commercial software with a first-class self-host option. On this list, Mattermost, Rocket.Chat, Zulip, Element and Nextcloud offer open-source editions.
A single-tenant Docker Compose deployment per instance. Backups are portable and SQLite-based; uploaded files live on the filesystem and are backed up with your standard volume snapshots. Self-hosted deployments come with deployment help on request.
Self-hosted and enterprise deployments are custom — talk to us. For reference, our cloud starts at €10 per user/month for Core, with optional add-ons.
It gives you the strongest position on data residency and third-party access: the data stays on infrastructure you control. Polybase is designed around GDPR principles; self-hosting doesn't replace your own compliance work, but it removes a whole class of questions about where messages physically live.
See what a self-hosted workspace replaces.
Book a 30-minute demo and we'll walk through the deployment model on your infrastructure — or start with the detailed Slack comparison.
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