YouTube's principal features are the capability to upload and distribute video clips of any rational length. Most available standard video formats and converted to low resolution Flash for release. User account is necessary to b made in order to view YouTube video. This account provides a profile page that serves as an index to the user's uploaded videos, and on which users may optionally disclose personal details, or "subscribe" to other users' videos and "friend" other users; these details are then displayed in their profile pages. Users can then comment on other users or more commonly on particular video. Comments by users are displayed in the relevant pages. One of the YouTube feature is it offers community called 'group' which user may join to assert specific interests. Groups provide a way to serialize video content as well as offering a text message interface similar to discussion boards or Usenet.