How to Self-Host Mattermost (Slack Alternative)

You want team chat that you control, but you do not want your “Slack alternative” to turn into a fragile box nobody understands six months from now.

Short version: To self host Mattermost, you run the Mattermost app on your own server, connect it to a database, put it behind HTTPS, and keep its files, backups, and updates under control. The hard part is not starting Mattermost once; it is making sure logins, uploads, email, certificates, and storage still work later.

What does it mean to self host Mattermost?

Mattermost is a team chat app: channels, direct messages, file uploads, notifications, search, and integrations. It is often described as a Slack alternative because it solves the same everyday problem: keeping team conversations in one place.

To self host Mattermost means the app lives on a server you control instead of inside someone else’s hosted workspace. Think of it like running your own office kitchen instead of renting a shared café table. You decide where the keys are, what is stored there, and who can come in.

That control comes with responsibility. Mattermost needs a few supporting pieces: a database for messages and users, storage for uploaded files, a domain name, HTTPS, email delivery, and backups. None of those are exotic, but they do need to fit together cleanly.

What do you need before installing Mattermost?

You need a server with enough breathing room. Chat is not just text. People upload screenshots, PDFs, logs, and videos. The app also keeps search indexes and database records, so storage can grow quietly in the background.

For a small team, the usual starting point is modest CPU, enough memory for Mattermost and its database, and disk space sized for uploads. If you are unsure how to think about CPU, RAM, disk, and traffic, this plain-English guide to server sizing may help: What size server do you need?

You also need a domain, such as chat.example.com. People should not have to remember a raw server address. The domain points visitors to the server, and HTTPS makes the browser trust the connection. If that part is new to you, start with how to point a domain at your server and how to get free HTTPS on your server.

Finally, decide how you want to run the app. Many people use Docker, which is a way to package an app with the pieces it needs so it behaves more predictably. If Docker still feels abstract, this primer explains it without assuming you are a sysadmin: Docker on a server for beginners.

How does Mattermost fit together on a server?

A self-hosted Mattermost setup is like a small shop with a front door, a counter, a back office, and a storeroom.

The front door is the reverse proxy. A reverse proxy is the part that receives web traffic for chat.example.com and passes it to Mattermost. It also handles HTTPS, so users see the padlock in the browser.

The counter is the Mattermost application itself. This is where users log in, read channels, post messages, and upload files.

The back office is the database, usually PostgreSQL. PostgreSQL stores users, teams, channels, messages, permissions, and settings. If Mattermost cannot talk to PostgreSQL, your chat app may load badly or not load at all.

The storeroom is file storage. Uploaded images, documents, and attachments must live somewhere persistent. “Persistent” means the files survive restarts, updates, and rebuilds. If uploads are kept in the wrong place, they can disappear when the app is replaced.

What usually breaks after Mattermost is installed?

The first common failure is HTTPS. If the certificate is wrong or expired, users may see browser warnings instead of the login page. The exact problem might look like “certificate has expired” or “NET::ERR_CERT_COMMON_NAME_INVALID”. That usually means the certificate does not match the domain or was not renewed properly.

The second common failure is the reverse proxy. If Mattermost is running but the front door cannot reach it, users may see 502 Bad Gateway. In plain English, that means the public-facing web layer knocked on the wrong internal door or found nothing answering.

The third common failure is file upload size. A team tries to upload a recording or export and gets 413 Request Entity Too Large. That means one layer in front of Mattermost is refusing the file before Mattermost can accept it.

The fourth common failure is email. Mattermost can run without email for a while, but invites, password resets, and notifications suffer. If email is not configured clearly, you end up with users who cannot join or recover access without manual help.

The fifth common failure is silent growth. Chat feels lightweight until uploads and database files fill the disk. When that happens, Mattermost can slow down, fail to write new messages, or stop cleanly restarting. Backups matter here too: a backup you have never restored is more like a wish than a safety net.

FAQ

Is Mattermost free to self-host? Mattermost has a self-hosted Team Edition that many small teams use. Paid editions add business features such as advanced compliance, administration, and enterprise identity options.

Can I run Mattermost and other apps on the same server? Yes, but keep each app separated clearly. One project should not be able to break another by fighting over domains, ports, storage, or certificates.

Do I need Docker for Mattermost? No, but Docker is a common choice because it makes the app, database, and supporting services easier to reason about as separate boxes.

**Why does Mattermost show 502 Bad Gateway?** Usually the reverse proxy cannot reach the Mattermost app. The app may be stopped, listening in the wrong place, or separated from the proxy by a mismatch in the setup.

How often should I back up Mattermost? Back up often enough that losing messages since the last backup would be acceptable. For active teams, that usually means regular automated backups of both the database and uploaded files.

The shortcut

Server Manager helps by keeping the moving parts understandable: the domain, HTTPS, app, storage, and database are not scattered across a pile of forgotten notes. The point is to reduce the chance that a wrong certificate, an expired certificate, or a hidden proxy mismatch turns into a morning of guesswork.

It also helps when the server has more than one project on it. Mattermost should not break because another app changed the shared front door, claimed the wrong address, or made the setup hard to read. The real benefit is that the arrangement stays legible over time, so you can come back months later and still understand what belongs to what.

Self-hosting Mattermost is worth it when you want control without turning chat into a mystery machine. When the domain, HTTPS, database, uploads, email, and backups all have a clear place, your team gets the simple win: private chat that keeps working.