Mattermost vs Zulip

Mattermost and Zulip are both self-hosted team chat servers that teams run instead of Slack, with web, desktop and mobile apps and a PostgreSQL database underneath. The deciding difference is how conversations are organised. Mattermost works like Slack: a channel is one stream of messages, and replies can fold into a thread. In Zulip, every message in a channel belongs to a named topic. After that come two practical questions: which free edition you actually get, and how much memory each one needs.

Channels with threads, or channels with topics

Mattermost follows the Slack model. Its docs say "replies to messages are collapsed under the first message of a thread. Open a thread by selecting the message or reply count". A Threads view lists the threads you follow, newest reply first. Messages that start outside a thread stay in the main channel flow.

Zulip makes the topic part of every message. Its help centre says "Topics in Zulip fill the role of threads in other chat apps", and that "there's nothing special about the first message in a thread. Instead, each thread is labeled with a topic". Threads appear in the main message view, not a side panel, and the left sidebar lists recent topics per channel. A topic can be marked resolved, which puts a ✔ in front of its name, so a channel can double as a lightweight queue for support questions or incidents. Zulip's README describes the design as working for "both live and asynchronous conversations".

This is a matter of habit, not a feature gap. A team that lives in Slack will find Mattermost familiar from day one. A team spread across time zones, where people catch up on hours of messages at once, is who Zulip's topics are built for. It also takes some getting used to: people have to name a topic when they post.

Which free edition you get

Zulip is Apache-2.0, and its pricing page says "all plans offer the same 100% open-source software". The self-hosted plans change support and one hosted service. Apple and Google do not let a self-hosted server send mobile push notifications to the Zulip apps directly, so they go through Zulip's Mobile Push Notification Service (end-to-end encrypted from Zulip Server 12.0). The free self-hosted plan covers "mobile notifications for up to 10 users" for most organisations, and without limit for eligible communities. Past that, the Basic plan is listed at $3.50 per user per month.

Mattermost's source is AGPL-3.0, but which binary you run matters more than the source licence:

• The official Docker repo's env.example sets MATTERMOST_IMAGE=mattermost-enterprise-edition (tag 11.7.0). Mattermost's docs say that once Enterprise Edition is installed "you can run it as-is in a free mode, known as Entry". Entry, new in v11, is under a commercial licence and is "best suited for teams less than 50 users". It keeps only "10,000 Channel messages history across all channels"; older messages "remain in the database but aren't viewable or searchable". The same list has a 40-minute Calls cap and 10,000 push notifications a month, which the docs say "will take effect in a future release".
• Team Edition (mattermost-team-edition, the other value that env.example names) is MIT-licensed and has no history cap. The docs describe it as for use "under 250 activated users where single sign-on (SSO) is not required".

If you install Mattermost from the Docker repo unchanged, you are running Entry. Decide which edition you want before the first message is sent.

What you run

Mattermost is a Go server with a React front end and PostgreSQL. The Docker repo runs two containers, the app and PostgreSQL (18-alpine in env.example), plus an optional nginx file for TLS. Mattermost supports PostgreSQL 14 and newer; the docs say "MySQL database support is being deprecated starting with Mattermost v11". Upstream sizes 1 to 1,000 users at "1 vCPU/cores, 2 GB RAM".

Zulip is Python and Django on PostgreSQL. The docker-zulip Compose file runs five containers: Zulip 12.3, PostgreSQL, memcached, RabbitMQ and Redis. The docs say Zulip "only serves content over HTTPS", and plain HTTP just redirects. The Docker image can make a self-signed or certbot certificate for you. Without Docker, the installer "expects Zulip to be the only thing running on the system", because it configures nginx, PostgreSQL and Redis for itself. Upstream asks for "at least 2 GB RAM" plus 2 GB of swap below 5 GB of RAM, and "4 GB RAM, and 2 CPUs" from 100 users.

Memory, measured

We measured both idle, right after install, on our GCP e2-standard-2 test box (Ubuntu 26.04). Mattermost used ~256 MB (2026-09-28), and Zulip ~3.3 GB (2026-09-29) across its five containers. The Zulip figure is above the 2 GB upstream allows for small teams, and it is why we list Zulip at 4 GB and Mattermost at 2 GB. Idle numbers say nothing about load, but on a small VPS, Zulip needs the bigger box.

Both installs on this site were tested on Ubuntu 26.04. Mattermost needs the data directories created and handed to UID 2000, and the base Compose file chained with either the without-nginx or the nginx file. Zulip needs six generated secrets, a hostname in SETTING_EXTERNAL_HOST (the docs say "a domain name, not an IP address"), an app:init run, and generate_realm_creation_link to create the first organisation. We rate both 3 out of 5 to deploy. Step-by-step guides are at deploy Mattermost on a VPS and deploy Zulip on a VPS.

Moving between them

Zulip documents imports from Mattermost, Slack, Rocket.Chat and Microsoft Teams. The Mattermost import starts from Mattermost's own bulk export tool, which exports "all public and private channel messages", run through mmctl on the Mattermost server. So trying Zulip does not mean abandoning your Mattermost history.

Which to choose

Choose Mattermost if your team wants chat that works like Slack, with threads when they need them, on a small server. It measured ~256 MB idle and upstream sizes it at 2 GB for up to 1,000 users. Choose your edition on purpose: Team Edition (MIT, meant for under 250 users without SSO) has no history cap, while the default Enterprise image runs as Entry and hides everything beyond the latest 10,000 messages.

Choose Zulip if your team works asynchronously and wants every conversation filed under a topic you can find and resolve later. You get the whole Apache-2.0 server with no feature tiers. Budget 4 GB of RAM, and plan for mobile push beyond 10 users to need a paid plan unless you qualify as a community.

Choosing between Zulip and Mattermost

Coming from Zulip, Mattermost's appeal is a lighter server and a layout people already know from Slack. Coming from Mattermost, the usual reasons to move are the Entry history cap and threads that are easy to lose. Zulip can import your Mattermost export. For a third option, see Mattermost vs Rocket.Chat.