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 telephone 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 and editing of previous messages. Offline messages were implemented in a beta of version 5 but removed after a few weeks without notification. The usual features familiar to instant messaging users to user profiles, online status indicators and so on are also included.