Migration Background
Everything below is based on the experience of the MidHard Games team, January 2026. Our case and thoughts (consider this a disclaimer ;) ). If this information helps you, we’re glad - that’s exactly why we put it together. Let’s go!
On December 19, 2025, Slack told us: “guys, you’re from Russia, we’re shutting you down in 30 days” (the original letter from Slack is below). They kept their promise - and deleted everything, and harshly. Not just “changed” the access level with an option to restore, but outright deleted. So don’t drag your feet if you’ve received your own “happy letter”.
We had been using Slack since 2016 - more than 9 years. In total, there were 266 users, with 98 active users at peak periods.
At first, we wanted to find some workaround to stay on Slack, but then we decided to use the situation as an opportunity. The goal was: replace Slack with something, and come out ahead - it’s just another (business) game ))
Benefits of Moving from Slack to Mattermost
What we ended up with We now have our own workspace that won’t be easy to kick us out of - if that’s even possible at all. We preserved the necessary chats with threads, files, and so on (export, import). Goal number 1 achieved - we stayed in our familiar, well-tuned processes.
A bit about money Now we have roughly the same functionality, but several times cheaper. (costs are rounded, for simplicity)
| Scenario | Team Size | Slack (per month) | Mattermost (self-hosted, per month) | Difference per month | Annual savings |
|---|---|---|---|---|---|
| Small team | 14 people | $126 | $127 | −$1 (roughly equal) | - |
| Medium team | 40 people | $360 | $127 | $233 | ≈$2,800 |
A nice side effect - the larger the team, the lower the cost per user. Significantly lower. Over the next 9 years we’ll save $25,000 or more - savings (pure profit) out of thin air. *Comparisons are approximate, based on average load per user, without uploading large files (for that we use other services - we use Google Workspace).
And these aren’t even all the benefits.
Control, security and quality With our own server, we now have more control and security. I won’t go into detail about our new “clever” setup - you’ll just have to take my word for it (or not) - but it’s definitely worth it, especially as “just” an extra bonus. This turned out to be a “pleasant discovery” during the migration.
Calls now work properly right in the chat In 2025, Slack started having problems with calls (we noticed issues with one carrier, but we all know how these blockages start ;-) ). This was getting in the way of work. We had to hold meetings in Telemost, for example - which is inconvenient when you could just press “huddle” (in Slack that means a video meeting or call). And that’s a significant bonus out of nowhere.
We implemented video calls via Jitsi.
How to Migrate from Slack to Mattermost
Step 1
We found a ready-made solution and exported everything from Slack. Note: there are file size limitations. This didn’t affect us - all large files should be stored in cloud storage anyway. We used the slackdump tool (both builds and source code are available).
Step 2
We got the hang of the export tool - there are some nuances. We got the export done correctly and the way we wanted it )), and recommend checking out the Mattermost export documentation.
Step 3
We rented a server. We looked at various options and chose Yandex Cloud.
Step 4
We deployed Mattermost on the server and configured it.
Step 5
We imported the necessary channels and user accounts from Slack into Mattermost.
Step 6
Mattermost doesn’t have a built-in video call solution. For video calls, we integrated Jitsi. For document preview, we chose Collabora.
Step 7
We settled in, got used to it, and kept making games )
Downsides of Self-Hosted Mattermost
First, the migration itself requires effort: sorting out hardware, software, transferring data, adding everyone to the new workspace, and so on. Second, you need to maintain it. If you already have a group of servers across different data centers, this is just routine work. We do, which is why we chose to migrate.
We still had to keep Slack for communicating with some partners on their own workspaces.
Original letter from Slack
Hello, Slack complies with the sanctions and export control laws of the United States, European Union, and other applicable jurisdictions, including restrictions on providing software and services to Russia. Our records indicate that your account is based in Russia, is predominantly used by users in Russia, or is otherwise connected to distribution in Russia. Unfortunately, in compliance with applicable law, we are therefore required to suspend your workspace … in 30 days.
Important and Useful Information About Mattermost
We’d heard about Mattermost as a Slack alternative for a while, but it turned out things aren’t quite so simple. In recent years, the company has significantly cut back the capabilities of free versions and changed their terms:
1 - Cloud Free plan discontinued Since July 2023, Mattermost discontinued the free tier for its cloud version (SaaS). Now you have to pay to use Mattermost in the developer’s cloud, or use the 30-day trial.
2 - Changes to Self-Hosted For those installing the messenger on their own servers, here’s the breakdown:
Mattermost Team Edition (Open Source): Remains free under the MIT/GNU AGPL v3.0 license, but in version v11 the user limit was reduced from 1,000 to 250. GitLab SSO integration was also removed from this version.
Mattermost Entry (Free): This is a new free commercial version for small teams (up to 50 people). It includes many enterprise features (SAML, AD/LDAP), but has strict usage limits:
- Up to 10,000 messages in history.
- Up to 10,000 push notifications per month.
- Call duration limit (up to 40 minutes).
3 - “Paid” features in free versions Users are complaining about “hidden” monetization of previously free features. For example, in version v10 the Calls plugin became free only for direct messages (1-on-1), while group calls in channels now require a paid subscription ($10 per user per month). More details on Reddit.
However, the project has a shared codebase, and the license allows building custom versions. Which makes it possible to enable the necessary functionality in your own build :D
Good luck to everyone with their migration, if the need arises. The main thing - don’t delay, and export your content from Slack’s servers as quickly as possible.