Mattermost vs OpenIM (2026): which should you pick?

Pick Mattermost if

• Fits if your chat has to stay on your own servers or on an air-gapped network
• Works for technical teams who can run and maintain their own server

Look elsewhere if

• Skip it if nobody on the team wants to run a server, as it's self-hosted by design
• Not for you if you want to see a price before talking to anyone, because every paid license is quoted by sales
• Tight if you rely on the free Entry mode, which only shows the latest 10,000 channel messages and has community support
• Watch out: Team Edition has no single sign-on, and the vendor doesn't recommend it for sensitive work
• Pricey if you need workflow automation or boards, as both start on Enterprise, sold as prepaid annual seats

Pick OpenIM if

• Fits if you are a developer who wants chat inside your own product
• Works for companies that will host their own messaging server

Look elsewhere if

• Not for you if you want a ready chat app, as the open-source part is for building one
• Watch out: Business and Enterprise prices are not published
• Watch out: voice and video are separate modules bought as needed
• Skip it if you do not want to self-host, since Kubernetes deployment is an Enterprise feature
• Too light for production without the commercial clients, as the site says Enterprise is for that

Mattermost

• No prices are published: Professional, Enterprise and Enterprise Advanced are quoted by sales and sold as prepaid annual seat subscriptions.
• Entry shows only the latest 10,000 channel messages and has community support only; the vendor suggests it for teams of fewer than 50 users.
• It is self-hosted by design; the only vendor-hosted option described is single-tenant Mattermost Cloud Enterprise, arranged through sales.
• Team Edition has no single sign-on, and the vendor does not recommend it for government or sensitive commercial workloads.

OpenIM

• OpenIM is not a single chat app. Open Source is meant for development and custom clients, and the site says Enterprise is for production.
• Business and Enterprise have no published prices; they are bought through a request-a-trial and contract process.
• Voice and video and video meetings are separate modules purchased as needed on the commercial editions.
• The open-source GitHub page lists an Electron demo app for Windows, Mac and Linux, but the site presents these as demos.

Mattermost

Channel-based messaging

1-1 and group messages, public and private channels, threaded discussions, file sharing and search across web, desktop and mobile, in 20 languages.

Playbooks

Repeatable playbooks for incident response, change management and compliance, with conditional checklists and escalation. The pricing page lists workflow automation from Enterprise.

Calls and screen sharing

1:1 audio calls with screen sharing are in every paid package, and group calls support about 50 concurrent users per self-hosted server. A 40-minute call limit is planned for Entry.

Boards

Kanban, table, calendar and gallery boards for assigning and tracking tasks next to the conversation. The pricing page lists work management from Enterprise.

AI agents

Agents summarize conversations and take actions using an LLM provider the customer chooses, or a self-hosted model in air-gapped environments.

Integrations and API

A REST API with an OpenAPI 3.0 spec, webhooks, slash commands and a plugin platform, with prebuilt integrations for tools such as Jira, GitHub and GitLab.

OpenIM

Chat and messaging

One-to-one chat, groups, large groups, message history, offline messages, receipts, search and multi-device sync.

Voice and video

Voice calls, video calls, group calls, video meetings and screen sharing, sold as separate modules for the commercial editions.

Client SDKs

SDKs for iOS, Android, web (JavaScript), Flutter and React Native, and the site says it covers 10+ client platforms.

Server API and webhooks

Server APIs and webhook callbacks connect accounts, permissions and events to your own backend.

Self-hosted deployment

OpenIM Server runs in your own cloud or private network, and Enterprise adds Kubernetes and a high-availability cluster.

Mattermost

• Entry$0

  Free mode of the Enterprise Edition: Enterprise Advanced features with 10,000 viewable messages, community support, and no compliance or high availability.

• Team Edition$0

  Open-source, MIT-licensed edition for small teams and personal use under 250 activated users, without single sign-on.

• ProfessionalCustom

  For teams of up to 250 users: single sign-on, AD/LDAP sync, guest accounts and next-business-day support. Sold as prepaid annual seats.

• EnterpriseCustom

  Adds workflow automation, work management boards, compliance and data retention tools, federated communications and high availability.

• Enterprise AdvancedCustom

  Adds zero-trust attribute-based access controls, classification banners, burn-on-read messages and support for air-gapped environments.

OpenIM

• Open Source$0

  OpenIM Server and IM SDK for development and custom client integration; you host it yourself.

• BusinessCustom

  Production-ready client UI on multiple platforms under a commercial license. No price is published.

• EnterpriseCustom

  Everything in Business plus advanced messaging, Kubernetes deployment and high availability. No price is published.

Mattermost

• Nonprofit

  3-year Professional license for $250

  Eligible nonprofit and open-source organizations can apply for a 3-year self-hosted Mattermost Professional subscription for up to 1,000 users for a $250 fee.

OpenIM

No public discounts listed.