Skype is the most popular free voice-over IP and instant messaging service globally. It allows users to text, video and voice call over the internet. Users can also call landlines and mobiles at competitive rates using Skype credit, premium accounts and subscriptions. Skype was publically released in 2003 and now accounts for roughly a third of all international calling minutes. Skype uses P2P technology to connect users on a multitude of platforms including desktop, mobile and tablet. The call quality (depending on your internet signal) and additional features like conversation history, conference calling and secure file transfer are excellent. There have been some criticisms over the programs bandwidth usage and security vulnerabilities.