Slack is indispensable for modern teams — but it is a US product owned by Salesforce, and every message your team sends is stored on US servers subject to the CLOUD Act. For EU companies handling sensitive business communications, client data, or any regulated information, this is a genuine compliance risk.
The good news: there are excellent EU-built and EU-hosted team messaging platforms that match Slack feature-for-feature — and in several cases exceed it — while keeping your conversations inside European jurisdiction.
Why Slack's data residency isn't enough
Slack offers a "Slack for Enterprise Grid" data residency option that stores messages in the EU. But data residency and data sovereignty are not the same thing. Slack is a US company: even when your data sits on European servers, Slack remains subject to US law and can be compelled to hand over data under the CLOUD Act or a National Security Letter — without notifying you.
The only way to eliminate this risk is to use a provider that is both headquartered in the EU and stores data in the EU.
Top EU-built Slack alternatives
Element / Matrix — open-source, self-hosted, federated
Element is a UK/EU-based messaging platform built on the open Matrix protocol. It is the closest open-source equivalent to Slack: threaded channels, direct messages, voice and video calls, file sharing, and integrations with tools like Jira and GitHub.
Key features:
- Open-source (Apache 2.0)
- Self-hostable on any EU infrastructure — run Synapse (the reference Matrix server) on a Hetzner VPS
- End-to-end encryption for direct messages and rooms (optional)
- Federated — your server can talk to other Matrix servers without sharing your data
- Element Cloud hosted in Europe (UK and EU regions available)
- Bridges to Slack, Teams, Telegram, IRC — migrate gradually without cutting off existing tools
Best for: teams that want full data sovereignty and are willing to self-host, or organisations that need end-to-end encrypted communications by policy.
Mattermost — open-source Slack replacement, EU-deployable
Mattermost is the most direct open-source Slack replacement available. The codebase is mature (used by the US Department of Defense and major European enterprises), the UI is deliberately Slack-like, and the self-hosted deployment on EU infrastructure gives you complete data sovereignty.
Key features:
- Channels, threads, direct messages, calls
- Slash commands, bots, and a rich app marketplace
- Slack-compatible import — migrate your entire workspace history
- Self-hosted on your own EU server; paid managed hosting available
- GitLab natively integrates Mattermost (if you're already self-hosting GitLab, you get Mattermost free)
- Granular compliance export for regulated industries
Best for: engineering teams and enterprises that need a Slack-compatible experience with full self-hosting control.
Zulip — structured async messaging, EU-deployable
Zulip is a US-founded but fully open-source team chat platform with a distinctive "topic-first" threading model. Rather than channels with loose threads, Zulip organises every message under a stream + topic pair — which makes async communication far easier to follow for distributed teams.
- Open-source (Apache 2.0) — self-host on any EU VPS
- Zulip Cloud is US-hosted, but self-hosted deployments on Hetzner or similar EU providers are fully EU-resident
- Excellent for async teams: topics make it easy to catch up without reading everything
- REST API and strong integration ecosystem
Best for: remote-first and async-heavy teams who find Slack's threading model chaotic.
Rocket.Chat — full collaboration suite, EU-hostable
Rocket.Chat is a Brazilian open-source platform (with EU hosting options) offering team chat, video calls, live chat (customer-facing), and a marketplace of integrations. It is one of the most feature-complete self-hosted alternatives to Slack.
Key features:
- Channels, DMs, threads, video and voice calls
- Customer-facing live chat widget (replaces Intercom for support teams)
- Omnichannel: email, WhatsApp, SMS, and social channels in one inbox
- Self-hostable on EU infrastructure; Rocket.Chat cloud can be configured for EU regions
- Slack import tool
Best for: teams that want to combine internal team chat and customer support in one self-hosted platform.
Comparing EU-friendly Slack alternatives
| Platform | EU-founded | Self-hostable | E2E encryption | Slack import | Free tier |
|---|---|---|---|---|---|
| Element (Matrix) | Yes (UK/EU) | Yes | Yes | Via bridge | Yes |
| Mattermost | No (US) | Yes | No (at rest) | Yes | Yes (CE) |
| Zulip | No (US) | Yes | No (at rest) | Yes | Yes (self-hosted) |
| Rocket.Chat | No (BR) | Yes | Partial | Yes | Yes (self-hosted) |
| Slack | No (US) | No | No | — | Limited |
Note: Mattermost, Zulip, and Rocket.Chat are US or non-EU founded, but their open-source licences allow you to self-host on EU infrastructure you own and control. Self-hosted deployments avoid the CLOUD Act problem entirely because the provider has no access to your data.
Recommended setup for EU teams
Smallest teams (under 20 people): Element.io cloud on their EU region — zero infrastructure overhead, end-to-end encrypted by default, and covered by a GDPR-compliant DPA. Free for small teams.
Growing teams with a developer: Self-hosted Mattermost CE on a Hetzner CX22 (€4/month). You get Slack parity, a Slack import tool to migrate your history, and complete data sovereignty. Pair with Hetzner Object Storage for file attachments.
Teams already using self-hosted GitLab: GitLab bundles Mattermost — enable it in your GitLab admin panel. One server, one DPA, no additional cost.
Compliance-sensitive organisations (finance, legal, healthcare): Self-hosted Element (Matrix/Synapse) with end-to-end encryption enforced at the room level. Gives you auditable, encrypted communications stored on infrastructure you own.
Migrating from Slack
Both Mattermost and Rocket.Chat provide Slack workspace export importers. The steps:
- Export your Slack workspace (Workspace Owner → Settings → Import/Export)
- Import the ZIP into Mattermost or Rocket.Chat — channels, messages, and users are migrated
- Reconnect integrations (Jira, GitHub webhooks, bots) — these use standard webhooks and work identically
- Invite the team and run both platforms in parallel for one week
- Deactivate the Slack workspace once the team has transitioned
The practical effort is a few hours of admin work plus the team adjustment period. Most teams complete the switch in two weeks.
Browse all EU-built team messaging and collaboration tools on EU Alts, or explore the full messaging category.