Skype is one of the best free voip websites has experienced rapid growth in both popular usage and software development since launch, both of its free and its paid services. The Skype communications system is notable for its broad range of features, including free voice and video conferencing, its ability to use peer to peer (decentralized) technology to overcome common firewall and NAT (Network address translation) problems, and its extreme countermeasures against reverse engineering of the software or protocol.

Skype also routes calls through other Skype peers on the network to ease the traversal of Symmetric NATs and firewalls. This, however, puts an extra burden on those who connect to the Internet without NAT, as their computers and network bandwidth may be used to route the calls of other users.