Viber is an all-in-one communication application for Windows PCs. You can share instant messages, make live audio or video calls, and express yourself through expressive stickers. It also facilitates you to communicate with your friends via group chats. Since the software runs in the background, it doesn’t waste system resources. The notifications appear in the system tray to keep you updated. All you need to do is to create your account with your mobile phone number and you can use this tool for free. Rakuten Viber launched this software in 2010 for smartphones and later released its desktop version to facilitate users.
Skype is a free communication application that works with desktop systems as well as mobile operating systems. You can make video or audio calls, send text messages, share emoticons, documents, images, multimedia content and much more.
Google Duo is a no-frills video calling app for Android and Apple devices. It is an alternative to Apple's Facetime and makes video calling easier between Android and iOS ecosystems. Google launched Duo just for Smartphones and tablets initially but it now works on computers as well.