A Slack alternative you own

Team chat

Team chat that stays inside your perimeter, with message history in your own database and sign-on from your directory.

Replacing: Slack, by Slack Technologies, LLC, a Salesforce company
With: Mattermost, Element
Runs on: Your servers, or Pilae Cloud in Switzerland and the EU
Migration: Included in onboarding, at a fixed price

Why teams leave Slack

Chat is where things get said

Incident threads, customer names, credentials pasted in a hurry. With Mattermost on your own machines, that history sits in your Postgres and nowhere else.

Reachable only on your network

Mattermost answers on the private mesh, behind one hardened gate. Staff reach it through the desktop and mobile apps; the internet does not see a login page.

Retention on your terms

How long messages are kept, who can export them and where the backups sit are your decisions, written into your contract rather than set by a vendor plan.

Slack vs Mattermost operated by Pilae

What is being compared	Slack	Pilae
Where messages are stored	In Slack infrastructure, with data residency regions available on eligible paid plans.	In your Postgres and object storage, on your premises or on dedicated machines in any of 12 Pilae Cloud regions, six of them in Switzerland and the EU.
Channels, threads and calls	Channels, threads, huddles, clips, canvases and Slack Connect between organisations.	Channels, threads, direct messages, voice and screen-share calls, and desktop and mobile apps.
Integrations	A large app directory with ready-made integrations, and workflow automation built in.	Slack-compatible incoming webhooks, slash commands and bots, plus n8n beside it for automations.
Sign-on	SAML SSO and SCIM provisioning on higher plans.	SAML or OpenID Connect sign-on through Keycloak or Entra ID. In Mattermost, single sign-on is part of the paid plans licensed by Mattermost.
Retention and export	Retention settings by plan; full exports of private channels and direct messages on higher plans, subject to Slack approval.	History in a database you hold and back up. Automated retention and compliance exports are features of the paid Mattermost Enterprise plans.
Operation	Fully run by Slack as a SaaS product.	Daily encrypted backups with monthly restore tests, planned upgrades by the Pilae Agent, 60-second probes.
Pricing	Per active user, per month, by plan.	On request, for the operated platform. The Mattermost licence your requirements need is shown separately in the proposal.

Self-hosted team chat

Slack is polished, fast and full of integrations, and most teams that leave it miss something. The reason they leave is usually the same: the most candid record of how an organisation works is held on someone else’s servers, under someone else’s retention rules.

Mattermost gives your staff channels, threads, direct messages, calls and mobile apps, on machines you control. Pilae deploys it on your premises or on dedicated machines in Switzerland and the EU, reachable only through the private network. The rest of the stack it sits in is on the sovereign workplace page. Where messages must be end-to-end encrypted, or rooms shared with partner organisations running their own servers, Element on Matrix is the other answer.

Moving off Slack without losing history

The history import is routine once the export is right, and the export depends on your Slack plan, so that is the first thing we check. Integrations are the part teams underestimate: we inventory every bot and webhook, move the ones that carry over and rebuild the rest in n8n. The move is part of our fixed-price migration, with sign-on set up through identity. Single sign-on in Mattermost needs a paid Mattermost plan, and we put that licence in the proposal rather than on a later invoice.

After the switch, the Pilae Agent plans each Mattermost upgrade, waits for your approval and applies it in your window. Pricing is on request. Tell us about your workspace and we come back with a plan.

Moving from Slack to Mattermost

Get the right export
Workspace owners on every plan can export public channels. Private channels and direct messages need a higher plan and Slack approval, so we start that request first.
Import the history
Users, channels, messages, threads and attachments come across with Mattermost import tools. Accounts are matched to your directory, so history lands under the right name.
Move the integrations
Incoming webhooks keep their payload format, so most alerting points at a new URL and works. Slack apps and workflows are rebuilt as Mattermost bots or n8n automations.
Switch on an agreed day, then close the workspace
Desktop and mobile apps are rolled out ahead, single sign-on is live, and Slack goes read-only on the day. The subscription ends at the next renewal.

The apps that replace Slack

Mattermost

Team chat, channels and calls on a server in the country you choose, with the message history stored in your own database.

Replaces Slack, Microsoft Teams

Element

Encrypted team messaging on the Matrix protocol: the Element apps on a Synapse homeserver you own, run in Switzerland, the EU or your own datacentre.

Replaces Microsoft Teams chat, Slack, WhatsApp

Questions

Can we import our Slack history into Mattermost?

Yes. Mattermost imports a Slack export: users, public and private channels, direct messages, threads and file attachments. How much history you get depends on the export your Slack plan allows, which we check before quoting.

Is Mattermost open source?

The source is: the server under AGPL-3.0, and the compiled Team Edition under MIT. Mattermost positions Team Edition for teams under 250 users and is removing single sign-on from it. Most organisations leaving Slack therefore need a paid Mattermost plan for sign-on, and the Enterprise plans for retention policies and compliance exports. We tell you which one in the proposal.

What about Slack Connect with other organisations?

Mattermost has no direct equivalent to a shared channel with an outside Slack workspace. Guests from partner organisations get guest accounts on your server instead, limited to the channels you choose. Element comes closer: Matrix federation lets one room span your server and a partner's, for the partner domains you put on an allow-list.

Will our alerting bots keep working?

Most will. Mattermost accepts Slack-format incoming webhooks, so monitoring tools and CI pipelines usually need only a new URL. Interactive Slack apps are rebuilt, and we list them in the inventory.

What happens to our messages if we leave Pilae?

They are in your Postgres and your object storage, and the compose files and runbook are in your repository. Mattermost also exports in its own bulk format.