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Jitsi is an open-source project and software toolset that allows you to easily build and deploy secure video conferencing solutions. At the heart of Jitsi are Jitsi Videobridge and Jitsi Meet, which let you have conferences on the internet, while other projects in the community enable other features such as audio, dial-in, recording, and simulcasting.  Jitsi supports popular protocols such as SIP, XMPP/Jabber, ICQ/AIM, Windows Live, Yahoo!, Google Hangouts, OTR, ZRTP and more.

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Pidgin is a chat application which lets you log into accounts on multiple chat networks simultaneously. Pidgin is developed and released fully free and open-source and provides a plugin architecture that allow anyone to build extensions and connections to new networks and third-party services.

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.