Open-source Flock alternatives

Rocket.Chat is a communications platform written in TypeScript for teams and organizations that care about data protection. It supports real-time conversations between colleagues, with partner companies, and with customers or citizens, and its topics place it in the same space as Slack, with WebRTC for calls and meetings.

The product emphasizes control over where and how it runs. Deployment options include self-hosted servers, a managed cloud and fully air-gapped environments, with a scalable architecture and performance monitoring for workspace administration. Security and sovereignty features, including identity management, are a core part of the pitch, and the platform is built to be highly customizable, so organizations can adapt it to their own workflows and integrations.

The repository's license is listed as 'Other' on GitHub, although the topics reference an MIT-licensed community core, so confirm which components fall under which terms before relying on it commercially. It suits government bodies, enterprises and regulated industries that want a Slack-style tool they can host themselves.

Mattermost is an open-core collaboration platform you host yourself, covering team chat, workflow automation, voice calls, screen sharing and AI integrations. This repository is the primary source for core development of the platform. The server is built with Go and React, ships as one Linux binary and depends on PostgreSQL. GitHub lists the license as 'Other'.

Each month, on the 16th, a newly compiled release is published under the MIT license. You can deploy Mattermost on-premises or try it in the cloud. The project highlights use cases such as DevSecOps, incident resolution and IT service desk, and it offers native clients for Android, iOS, Windows, macOS and Linux in addition to the web interface.

Installation options include Docker, Ubuntu, a tar archive, Kubernetes, Helm and an Omnibus package. Developers can build integrations through APIs, webhooks, slash commands, Apps and plugins, and the repository links product and developer documentation, security bulletins and contribution guides. It suits engineering, security and operations teams that want controlled, self-managed team messaging.

Zulip is an open-source team chat application whose defining feature is topic-based threading within channels. The idea is to blend the strengths of email and chat, so that remote and distributed teams can follow several conversations at once and catch up later without losing context. Its topics tag it as a Slack alternative.

The project is developed by a distributed community, with more than a thousand contributors and a steady flow of commits each month, and it says it has put effort into readable, tested code and extensive contributor documentation. The server is a Python web application, and there are web, desktop, built on Electron, and mobile clients, built with React Native. Zulip is used by companies and open-source projects alike, and the README says it is designed for both live and asynchronous communication.

Zulip is licensed under Apache-2.0. You can run the server on your own infrastructure, which gives full control over data, or use the hosted service operated by the project's company. It suits teams that find flat channel-based chat chaotic and want a more structured way to keep discussions organized.

Element Web is a client for Matrix, the open protocol for decentralized messaging. It is the web and desktop application formerly known as Vector and Riot, and it lets people join rooms, chat in teams and communities, and collaborate across Matrix servers rather than inside a single vendor's network.

The client is built with TypeScript on top of the Matrix JS SDK. The README defines support tiers for browsers, covering recent versions of Chrome, Firefox, Edge and Safari on desktop, best-effort handling for ESR and extended-stable releases, and community support for mobile web. For phones and tablets the maintainers recommend the native Element X apps for Android and iOS.

It is released under the AGPL-3.0 license and is typically served from your own web host or used through the hosted app from the vendor, Element. Related products such as Element Call and the Enterprise Server Suite are mentioned as part of the wider Element offering. Changes are tracked on GitHub with regular release cycles.

Campfire is a web-based group chat application that Basecamp offers as software you run yourself, with no subscription. It covers the features people expect from team chat, including multiple rooms with access controls, direct messages, @mentions and search.

Files can be attached to messages and previewed, notifications are delivered via Web Push, and an API supports bot integrations. The Docker image bundles the web app, background jobs, caching, file serving and SSL, so a single machine is enough for a complete deployment. A pre-built image is published on the GitHub container registry.

The simplest way to deploy is ONCE, a tool that walks through setup and keeps the instance up to date automatically; you can also run the Docker image directly by following the self-hosting guide. On first launch a wizard creates the admin account, whose email address appears on the sign-in page. Campfire is written in Ruby, licensed under MIT, and open to modification.

Openfire is a real-time collaboration server that implements XMPP, also called Jabber, which the project describes as the only widely adopted open protocol for instant messaging. It is written in Java, released under the Apache-2.0 license and maintained as an Ignite Realtime community project.

The project says Openfire is easy to set up and administer while still offering strong security and performance. Organizations use it to run their own messaging infrastructure instead of relying on a proprietary chat vendor, and because XMPP is an open standard, any compatible client can connect to it.

Support is community-based. Documentation lives on the Ignite Realtime site, discussion happens on a Discourse forum, and bugs are tracked in an issue tracker where new users are asked to post through the forum first. Nightly builds are available, translations are managed through Transifex, and the latest release listed is v5.1.2.

Chatto is an open-source chat application for teams and communities that is meant to be free and easy to self-host. The repository contains the chat server, a command-line tool, and a bundled web front end, and the project describes itself as fully featured. It is released under the AGPL-3.0 license.

The topics describe a privacy-first design that is GDPR-compliant, and the application includes voice calls, video calls, and screen sharing in addition to text chat. The repository also hosts related components, including Runling, an independent workflow and agent orchestrator published on npm, and Authling, an identity provider that is expected to move to its own repository.

The README says cloud hosting will be available soon, so self-hosting is the supported route today, with a documentation site and releases for installation. The authors note that Chatto is built with the help of coding agents. It is a young project created in 2026 and suits teams that want an alternative to hosted workplace chat tools.

This repository is the web client of VoceChat, a chat product whose server you can host yourself. The client is a TypeScript single-page app built with React and Redux Toolkit, delivered as a progressive web app, and it uses Firebase for notifications. It is released under the GPL-3.0 license.

To use it you either host your own Voce server, which is available as a Docker image for x86-64 platforms, or connect to the project's test server. The README links to the official documentation for server hosting, a live demo, a Swagger API reference for the demo server, a Figma design file, and the editors used for rich text and Markdown. Local data is cached in the browser through IndexedDB with localForage.

VoceChat suits teams and communities who want a lightweight private messenger they run on their own infrastructure, and developers who want a web client they can modify or white-label. The topics also mention bots, so automated integrations are supported.

Mezon describes itself as a live, work, and play platform for communities and teams, suitable for gaming with friends as well as global communities and work use. You can customize your own space for talking and hanging out. The project covers chat, communication, communities, and a bot framework, and the input does not state a license.

The README says the performance comes from owning the whole path: native Android and iOS clients rather than hybrid ones, a Rust desktop app that renders its interface on the GPU, and a high-performance server. It makes claims of sub-millisecond response times and support for millions of concurrent connections, which are the vendor's own and not independently verified. The code is mostly TypeScript.

A bug report community and documentation are provided. Mezon suits teams and online communities looking for an alternative to Discord or Slack-style tools, particularly those interested in a lightweight desktop client and bot integrations.

Colanode is an all-in-one collaboration platform built around data privacy and control. It combines real-time chat, rich-text pages for documents, wikis and notes, customizable databases and file management in one workspace, positioned as an open-source alternative to Slack and Notion.

It has a client app, available on the web and as an Electron desktop app, and a self-hosted server. One app can connect to several servers, each holding one or more workspaces for different teams or projects. Databases support custom fields and table, kanban and calendar views. The local-first design writes every change to a local SQLite database first and syncs it in the background, so reads are immediate and people can keep working when offline.

The topics reference CRDTs and Yjs for real-time collaboration. Colanode is written in TypeScript and licensed under Apache-2.0, and because you run the server yourself you decide where the data is stored. It suits individuals, small projects and larger teams that want to avoid depending on a hosted vendor.