Continuwuity

Rocket.Chat is an open-source, secure, fully customizable communications platform for team collaboration and organizational messaging.

Novu is an open-source notification platform that provides a unified API and embeddable inbox for sending and managing multi-channel notifications.

Mattermost is a self-hosted collaboration platform for chat, workflow automation, voice calling, screen sharing, and AI integration.

ntfy is a simple HTTP-based pub-sub notification service for sending push notifications to phones or desktops via scripts and PUT/POST requests.

An open-source, self-hosted customer support platform for managing conversations across channels.

Zulip is an open-source team chat app with topic-based threading designed for both live and asynchronous conversations.

LiveKit is an open source, scalable WebRTC media server for building real-time video, audio, and data experiences.

Apprise is a notification library and command-line tool that sends messages to a wide range of third-party notification services.

A self-hosted server for sending and receiving real-time messages and notifications.

Tinode is a full-stack instant messaging server with native clients for web, Android, iOS, and command-line use.

Element is a Matrix web and desktop client.

A private messaging platform with no user identifiers, offering encrypted chat, groups, and calls across mobile and terminal apps.