Migration guide

How to migrate from Slack to Mattermost

How complete {from}'s export is depends on your plan: Free/Pro plans only export public channels, with no DMs or private channels — if you need that history, you need to be on a Business+ plan or higher before exporting.

1. 1

   Confirm your Slack plan's real export scope before promising anything

   In Workspace Settings → Import/Export Data, check what kind of export your current plan actually offers. If your team expects to recover DMs or private channels and you're on Free/Pro, it's not going to happen — settle this before announcing a cutover date.

2. 2

   Export Slack's history

   Generate the export from that same panel — Slack delivers a .zip with one .json per channel per day, plus `users.json` and `channels.json` metadata. You don't need to unzip it before uploading it to Mattermost.

3. 3

   Deploy Mattermost via Docker Compose

   Mattermost needs PostgreSQL (see the docker-compose.yml on its page). Before importing, create the accounts for the users you're migrating first — Slack's importer links messages to existing users by email, it doesn't automatically create new accounts in every case.

4. 4

   Import with mmctl, not just the web console

   As a system admin, use the `mmctl` CLI: `mmctl auth login`, then `mmctl import upload slack-export.zip`, `mmctl import list uploads` (note the ID it returns), and `mmctl import process <id>` to kick off the job. One-click import from System Console exists, but in several Mattermost versions it's an Enterprise feature — the CLI path works on the Team/OSS edition.

5. 5

   Reconnect integrations and check external shared channels

   Slack's webhooks, bots and connected apps don't migrate — you'll need to recreate them pointing at Mattermost. Slack Connect channels (shared with other companies) also have no automatic equivalent: those conversations stay only in Slack.

These steps are a general guideline — the exact export menu can vary depending on Slack's plan and version.