Slack

Freemium

Slack is a cloud-based team collaboration tool.

Discord

Free

Discord is a freeware proprietary VoIP application designed for gaming communities.

Glip

Freemium

Glip is fully searchable, real-time group chat; video chat, task management, file sharing app.

Matrix.org

Open Source

Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with…

Flock

Freemium

Flock is a communication app for teams. Packed with tons of productivity features, Flock drives efficiency and boosts speed of execution.

Zulip

Open Source

Zulip is a chat and collaborative software.

Gitter

Freemium

Gitter is an open source instant messaging and chat room system for developers and users of GitHub repositories.

Viber

Freemium

Viber Free Messenger and Phone Calls.

Jitsi

Open Source

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Rocket.Chat

Open Source

Rocket.Chat free open source chat solution.

TribeScale

Free

TribeScale is an All-in-One platform to coordinate your team around what really matters - communication, goals, decisions, tasks and results.

Grape

Commercial

Grape is an REST-like API framework for Ruby. It's designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by prov…