Slack

vs

Matrix.org

A VoIP application and platform designed for creating communities and connecting gamers, and people rallying around specific causes. The Discord client is a free to use and can handle text, image, video and audio communication between users in a chat channel. Currently over 250 million users use the software to connect with others across the globe.

Mattermost is an open-source, self-hostable enterprise team collaboration and messaging application. The software can be deployed to on-premis or to cloud instances. Mattermost is designed for internal use within organizations and businesses in financial services, government, healthcare, remote work, and enterprise DevOps, where teams use Mattermost to power collaboration at every stage of the DevOps lifecycle.

Microsoft Teams is your hub for teamwork, it brings together everything a team needs from chat and threaded conversations, meetings & video conferencing, calling, and content collaboration. With you can instantly go from group chat to video call with the touch of a button. Securely connect, access, share, and coauthor files in real time. While staying organized by keeping notes, documents, and your calendar together.

WeChat connects a billion people with voice calls, video calls, photo sharing, chats and payments. The multi-purpose application is developed by the Chinese company Tencent and is and in China, it is described as "the app for everything". WeChat is primarily developed for the mobile consumer, but is also avalible on desktop and in the browser.

Facebook Messenger is a free standalone chat application that is well integrated with the social network, Facebook. With Facebook Messenger you can stay in contact with friends and family, and other contacts from Facebook. The applicaiton has a ton of built-in features that make communication fun and engaging. Send images, gifs, video messages, voice notes, and stickers or share content from around the web. Facebook Messenger automatically syncs with your Facebook contacts without the need of adding phone numbers or identification manually.

A mobile group messaging app developed and owned by Microsoft. GroupMe was first launched in 2010, today the application has over 12 million registered users that engage in group communication. The application makes it easy to stay in touch with those who really matter to you, and to do so in groups.