Registered users of Skype are identified by a unique Skype Name, and may be listed in the Skype directory. Skype allows these registered users to communicate through both instant messaging and voice chat. Voice chat allows calls between pairs of users and conference calling, and uses a proprietary audio codec. Skype's text chat client allows group chats, emoticons, storing chat history, offline messaging and (in recent versions) editing of previous messages. The usual features familiar to instant messaging users — such as user profiles, online status indicators, and so on — are also included.



The SkypeIn service allows Skype users to receive calls on their computers dialed by regular phone subscribers to a local Skype phone number; local numbers are available for Australia, Brazil, Chile, Colombia, Denmark, the Dominican Republic, Estonia, Finland, France, Germany, Hong Kong, Hungary, Ireland, Italy, Japan, Mexico, New Zealand, Poland, Romania, South Africa, South Korea, Sweden, Switzerland, the Netherlands, the United Kingdom, and the United States. A Skype user can have local numbers in any of these countries, with calls to the number charged at the same rate as calls to fixed lines in the country.



Video conferencing between two users was introduced in January 2006 for the Windows and Mac OS X platform clients. Skype 2.0 for Linux, released on March 13, 2008, also features support for video conferencing. Version 5 beta 1 for Windows, released 13 May 2010, offers free video conferencing with up to 5 people.



Skype for Windows, starting with version 3.6.0.216, supports "High Quality Video" with quality and features, e.g., full-screen and screen-in-screen modes, similar to those of mid-range videoconferencing systems. Skype audio conferences currently support up to 25 people at a time, including the host.



A discontinued feature called "Skypecasting" allowed recordings of Skype voice over IP voice calls and teleconferences to be used as podcasts, which allow audio or video content to be syndicated over the Internet. Skype launched its "Skypecasts Beta" service in 2006. It remained in beta until its end. Skypecasts hosted public conference calls, up to 100 people at a time. Unlike ordinary Skype p2p conference calls, Skypecasts supported moderation features suitable for panel discussions, lectures, and town hall forums. Skype operated a directory of public Skypecasts.



On August 26, 2008, Skype announced that Skypecasts would be discontinued beginning September 1, 2008. Skypecasts were shut down without any concrete explanation on 1 September 2008 at 12:00 UTC. In late 2009 the company Skype for Power Gamers announced that in Q2 2010 it would be releasing both a client and server Skype Add-on that will enable Skype end-users to host their own "Skypecast-like" auto-conference rooms.



Skype does not provide the ability to call emergency numbers such as 911 in the United States and Canada, 111 in New Zealand, 000 in Australia, 112 in Europe, or 999 in the UK. The U.S. Federal Communications Commission (FCC) has ruled that, for the purposes of section 255 of the Telecommunications Act, Skype is not an "interconnected VoIP provider". As a result, the U.S. National Emergency Number Association recommends that all VoIP users have an analog line available as a backup.