Programs like Skype or Viber take advantage of VoIP technology (Voice Over Internet Protocol) to make free calls making use of an Internet connection. Despite being two of the most popular services, they're not the only ones of this nature. There are other more humble platforms that are equally efficient, as is the case of MicroSIP.

Open source alternative to Skype or Viber

It's a very lightweight application that can establish a communication between users with a SIP account. Resource consumption is minimal and the program has access to a vast amount of servers.

• Minimalistic and functional interface.
• Low memory consumption (less than 5MB).
• Voice and video calls and instant messaging.
• Compatible with the vast majority of SIP standards.
• Configurable privacy.

What is SIP?

SIP is the acronym for Session Initiation Protocol, an open source standard developed with the intention of making it the session initiation, modification and termination system for interactive user sessions in which multimedia elements such as videos, instant messaging, virtual reality, online games or voice take part.