Best Cross-platform Instant Messaging Apps

Signal is a cross-platform encrypted messaging application that has a strong focus on privacy. The application is developed by Signal Messenger LLC and provides users with features like one-to-one and group messages, which can include files, voice notes, images and videos. The software is famous for being used by the whistleblower and privacy advocate Edward Snowden who once said "I use Signal every day, it is the most scalable encryption tool we have".

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With Telegram people can communicate and via instant messaging and voice over IP. Telegram is a cloud-based software and services that have a focus on privacy, speed and security. The client was initially created by the brothers Nikolai and Pavel Durov, the creators of the Russian social network VK back in 2013. Today the application is used cross-platform by over 400 million users world-wide.

Slack is a new way to communicate with your team in a faster, better organized, and more secure than email. The software is designed for business looking to improve their communication work flow. Slack offers features like persistent chat rooms organized by topic, private groups, and direct messaging that is built for teamwork.

Viber is a cross-platform voice over IP application that allow people to make free and secure calls and messages to anyone, anywhere. With Viber, you can create group chats and make group calls, send stickers and emojis over chats that are 100% synced between devices, including 1-tap transfer of calls. Viber is available for free on Android, iOS, macOS, Linux and Windows.

A free, unlimited and open-source chat software. Rocket.Chat have set out to be a replacement for email, HipChat & Slack and is provided as Software-as-a-Service (SaaS) or a self-hosted community edition. Rocket.Chat is feature packed and can be used for video conferencing, file sharing, voice messages and more. The software integrates with third-party services like GitHub, GitLab, JIRA, and Confluence and provides an API that can be used for authentication and integration across these services.

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.

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.

WhatsApp is free messenger app for chat and voice over IP, owned and managed by Facebook. The application allow users to send text and voice messages, make voice and video calls and share images, media files and user locations with friends and family.

With Google Hangouts, you can keep in touch with through chat, video or voice calls in person or as a group. Google Hangouts is a cross-platform messaging app developed by Google that is available for Android, Chrome OS, iOS, Google Chrome or any browser that is compatible with Google Chrome Extensions.

Skype is a telecommunications application that specialize in providing video chat and voice calls between computers, tablets, mobile devices and consoles. The software allows you to connect with friends and business colleges worldwide. Skype provides free online calls, messaging, affordable international calling to mobiles or landlines and Skype for Business for effective collaboration among teams.