Mattermost vs Rocket.Chat

Both Mattermost and Rocket.Chat exist to answer the same question: how do you leave Slack without handing your team's entire conversation history to someone else's cloud? They are the two heavyweight open-source answers, and they are genuinely close on the things that matter day to day — channels, threads, DMs, mobile apps, and integrations. The real decision is not features on a comparison grid but temperament: do you want a fast, focused chat app that feels like the Slack your team just left, or a single platform that folds voice, video, and customer messaging into one deployment?

Two philosophies of "team chat"

Mattermost takes the focused route. It is, deliberately, a very good chat application: channels and threads, a clean and quick web client, a solid mobile app, slash commands, webhooks, and a plugin system for the extras. The experience is close enough to Slack that most people migrating never have to relearn how they work, and the product stays lean because messaging is the main event rather than one tab among many.

Rocket.Chat takes the platform route. Out of the box it is not just chat but a communications hub: an omnichannel module that turns the same inbox into a customer-support channel across the web, email, and messaging apps, plus a large marketplace of apps and integrations. If your goal is "one place for internal chat and talking to customers," Rocket.Chat wants to be that place without a second product bolted on.

Neither approach is wrong. They optimize for different owners — one for a team that wants Slack-without-Slack, one for an organization that wants a single messaging platform to run several conversations at once.

The stack difference is the operational story

This is where the two diverge most for a self-hoster. Mattermost is a compiled Go server with a React front end, backed by PostgreSQL. That means a single static binary (or one lean container) plus a boring, well-understood relational database — a stack most people running a VPS already know how to back up, tune, and upgrade.

Rocket.Chat is a Node.js application built on MongoDB, and in practice it wants MongoDB configured as a replica set even for a single-node install because it relies on the oplog to push messages in real time. That is entirely workable — the official Compose file sets it up for you — but it is a heavier, less familiar moving part than Postgres, and MongoDB is the piece most likely to need attention as your data grows. If you are comfortable operating Mongo, this is a non-issue; if you are not, it is the single biggest reason a Rocket.Chat box needs more babysitting over time.

Feature-by-feature

• Everyday chat — a near tie. Channels, threads, DMs, reactions, search, and file sharing are all solid on both. Mattermost feels a touch snappier and more Slack-like; Rocket.Chat exposes more knobs.
• Voice and video — neither ships it in the core, and we had this the wrong way round before. Rocket.Chat's docs list its call providers — Pexip, Jitsi, BigBlueButton, Google Meet — as apps "available as apps on the marketplace", and several call features (participant list, call history, ringing) are Starter/Premium-only. Mattermost's Calls plugin is a plugin, but a pre-packaged one: you enable it in the System Console rather than install it. 1:1 calls with screen sharing are available to everyone (capped at 40 minutes on the free editions); group calls up to 50 participants need a paid Mattermost plan. Call it a wash, with Mattermost marginally less to assemble.
• Omnichannel / customer messaging — a Rocket.Chat specialty with no direct Mattermost equivalent. If you want to talk to customers and colleagues from one server, this is the differentiator.
• Integrations and bots — both have webhooks, slash commands, and app ecosystems. Mattermost leans developer-workflow (CI, incident response); Rocket.Chat leans breadth of connectors.
• Migrating from Slack — both import Slack exports, but Mattermost's interface is the closer visual and behavioral match, which shortens the "where did everything go" phase for a switching team.

Resources and performance

The spec table now carries each project's own documented floor, and they are not the same number. Mattermost publishes 2 GB for 1–1,000 users. Rocket.Chat's smallest published scenario — Starter, no HA, up to 500 concurrent users — asks for 2 vCPU / 4 GiB for the app plus 2 vCPU / 4 GiB for MongoDB, so 8 GB is the honest figure to budget, and it is roughly four times Mattermost's. Both still rate 3/5 to deploy; neither is a lightweight you run next to a dozen other services. The difference is not just the number on the sheet but what fills it. Mattermost's Go binary is frugal and predictable under load, and Postgres behaves the way you expect. Rocket.Chat's Node plus MongoDB combination tends to sit higher at idle and is more sensitive to how Mongo is configured. Give either real headroom once a team actually lives in it, but expect Mattermost to stay lighter for the same number of active users.

Licensing

Both are open core, and the short labels flatter them. Rocket.Chat's root LICENSE puts everything under apps/meteor/ee/ and ee/ under a proprietary Rocket.Chat Enterprise Edition licence that requires a paid subscription in production; MIT (Expat) covers what is left. Mattermost's is the mirror image: AGPL-3.0 for the server source, Apache-2.0 for config and admin tooling, MIT for the binaries Mattermost, Inc. compiles — and server/enterprise/ under a Source Available licence that also requires a paid plan in production. For a team simply running either on its own VPS the licence text rarely changes anything; the free plans' limits matter more. Rocket.Chat's free Starter plan caps a workspace at 50 users (its Community option at 100 concurrent users, core messaging only), while Mattermost's free Entry mode keeps only the latest 10,000 channel messages viewable, and its Team Edition is aimed at teams under 250 users. If you plan to build a product on top of the code, Rocket.Chat's MIT core is the more permissive starting point — but check which directory the feature you need lives in first, on either side.

Which should you self-host?

Pick Mattermost if…

• You want a fast, Slack-like chat your team adopts with almost no relearning, and messaging — not a platform — is the point.
• You would rather operate a Go binary on PostgreSQL than run and maintain a MongoDB replica set.
• You value predictable resource use and a clean upgrade path for a stack you probably already know.

Pick Rocket.Chat if…

• You want omnichannel customer messaging in the same deployment as internal chat, not a chat app plus a separate support tool.
• You have 8 GB to give it, per Rocket.Chat's own system requirements.
• The broad app marketplace and deep configurability appeal to you more than a lean, opinionated core.
• You are comfortable running Node and MongoDB, and an MIT core (with a proprietary ee/ tree beside it) suits how you plan to extend the code.

Running either on a VPS

These are not the same size of server. Mattermost documents a 2 GB floor and lives comfortably there for a small team; Rocket.Chat's own requirements put the app and MongoDB at 4 GiB each, so plan for an 8 GB box rather than discovering it under load. The practical gap is operational: Mattermost's Go-and-Postgres stack tends to stay lighter and asks less of you over time, while Rocket.Chat's Node-and-MongoDB setup wants a little more care, especially around the database. The step-by-step setups are linked below, and any of the VPS options here has plenty of room for the app plus its database. If your community needs threaded, searchable discussion more than chat, see Discourse vs Flarum.