Zulip Alternatives for Mac OS X

Skype is an instant messaging and VOIP (Voice Over Internet Protocol) client to communicate with people in a distant place.

Telegram is a free cloud-based instant messaging platform.

Slack is a cloud-based team collaboration tool.

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Trillian is a proprietary multiprotocol instant messaging application.

Viber Free Messenger and Phone Calls.

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

Signal is the most scalable encryption tool.

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

LINE is a new communication app which allows you to make free voice calls and send free messages whenever and wherever you are.

Mattermost is an open source, private cloud Slack-alternative, Workplace messaging for web, PCs and phones. MIT-licensed.

Wire is a cross-platform, encrypted instant messaging client created by Wire Swiss. It is available for iOS, Android, Linux, Windows, macOS and Web browser clients.

ICQ is an open source instant messaging software.

WeChat is a social media with instant messaging, commerce and payment services application.

Rocket.Chat free open source chat solution.

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

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 users of a different service provider via online chat, Voice over IP, and Videotelephony.

KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features.

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

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

Zoiper is an easy to use sip video softphone, with excellent voice quality and easy to setup.

Tencent QQ (QQ) is an instant messaging software service.

QuteCom (WengoPhone) is a free-software SIP-compliant VoIP client.

Dialog Messenger is a handy and feature-rich enterprise multi-device messenger available for server or cloud.

Wickr is an instant messenger application.

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

Tkabber is a GPL instant messaging client for the XMPP protocol which uses the Tk toolkit for the GUI.

MySMS is a family of applications helps you text anywhere and enhances your messaging experience on your smartphone, tablet and computer.

Toky is an automation platform.