Group calls on self-hosted Mattermost

Free Mattermost gives you 1:1 audio calls with screen sharing. Invite a third person and the call refuses them. Mattermore removes that refusal on a self-hosted server, using a switch that Mattermost itself already ships in the calls plugin. No patched licence code, no database changes, and a rollback that takes two minutes.

What blocks Mattermost group calls today

The behaviour is narrow and specific. A direct call between two users works. Screen sharing works. A third participant is rejected before any media is negotiated.

That rejection is a licence check inside the calls plugin, not a limitation of the media stack. The WebRTC layer, the signalling and the session handling are the same code used for calls with many participants. The only thing standing between a two-person call and a group call is a boolean.

So enabling mattermost group calls on a self-hosted server is not a case of forcing software to do something it was not built for. It is a case of using a switch that upstream wrote and left reachable.

The switch upstream already ships

The check lives in GroupCallsAllowed() in server/enterprise/license.go. It returns true in either of two cases:

1. The server carries a Professional licence or higher.
2. The environment variable MM_CALLS_GROUP_CALLS_ALLOWED is set to the string true.

That second branch is present in every released version of the plugin, and it is read at runtime by the shipped binary. Setting the variable is enough on its own. Nothing needs to be recompiled to get past the check.

So the honest framing of mattermost group calls without licence is this: the capability is already in the software you are running. Mattermore’s job is to make that practical and to keep it turned on.

Why a plugin bundle is still involved

If the environment variable does the work, why ship anything at all?

Because Mattermost prepackages the calls plugin with the server. On startup the server reinstalls the prepackaged copy over an installed plugin when the prepackaged version is strictly higher, so a server upgrade can quietly replace what you put there.

Mattermore versions its bundles as 1000.<upstream version>, which keeps the installed version above anything the server will try to prepackage. The bundle keeps the plugin id com.mattermost.calls, so it is a drop-in replacement: clients, webhooks, integrations and existing call settings do not know the difference. It is also reversible. Remove the bundle, restore the upstream plugin, unset the variable, and you are back on stock Mattermost.

Setting up a Mattermost self hosted group call

The requirements are short:

• Mattermost v11.0 or later, self-hosted. Mattermore does not work on Mattermost Cloud, which allows neither plugin uploads nor custom environment variables.
• System administrator access to the System Console.
• The ability to set an environment variable on the process and restart it.

Step by step instructions are on install. Settings that matter afterwards are on configuration.

Networking: the part that actually breaks

Most failed mattermost self hosted group call setups are network problems, not plugin problems.

Calls media needs UDP port 8443 reachable from clients to the server, with TCP 8443 as a fallback when UDP is blocked. Media does not travel through your reverse proxy: nginx, Traefik or a load balancer terminating HTTPS on 443 handles the web application and the signalling, and has nothing to do with the audio path.

If two-person calls work but group calls drop participants, check the firewall and any NAT in front of the server before you look at the plugin. See troubleshooting.

How many people fit in one call

The practical ceiling is roughly 50 participants per call on a single server. That is a planning figure, not a limit enforced in code: real capacity depends on your CPU and uplink.

Screen sharing behaves in group calls exactly as it does upstream. Camera video is a different question, covered on video calls, where the constraints are tighter.

Where this leaves your licence

Mattermore is AGPL-3.0 and modifies AGPL-3.0 code only. The full reasoning is on licensing.

If you are weighing this against buying mattermost calls professional licence seats, be clear about what you are comparing. A Professional licence buys far more than group calls: compliance features, support and the rest of the commercial feature set. Mattermore buys group calls on an unlicensed self-hosted server, and nothing else.

Frequently asked questions

How do I enable group calls in Mattermost?

Set the environment variable MM_CALLS_GROUP_CALLS_ALLOWED to true on the process running your Mattermost server, restart it, and install the Mattermore bundle so a server upgrade does not overwrite the plugin. See install.

Can you have group calls in Mattermost without a licence?

Yes, on a self-hosted server. The calls plugin checks for a Professional licence or the MM_CALLS_GROUP_CALLS_ALLOWED environment variable. Setting the variable satisfies the same check.

Why does Mattermost only allow 2 people in a call?

A licence check in the calls plugin refuses the third participant. The media stack itself is not limited to two people, which is why removing the check is enough to get group calls.

How many people can join a Mattermost call?

Around 50 participants per call on a single server is a realistic ceiling. Video and heavy screen sharing will bring that number down before audio alone does.

Does Mattermore work on Mattermost Cloud?

No. Cloud does not allow plugin uploads or custom environment variables. You need a self-hosted server running v11.0 or later.

Will a Mattermost upgrade undo this?

Not with the Mattermore bundle installed. Mattermost reinstalls its prepackaged calls plugin only when its version is strictly higher than yours, and Mattermore versions itself 1000.<upstream> to stay above it. See docs.

Do I need to open any firewall ports?

Yes. UDP 8443 must be reachable from clients, with TCP 8443 as a fallback. Media does not pass through your reverse proxy, so an HTTPS proxy on 443 is not enough.