Freestyle swimming is a type of competitive swimming. The rules allow swimmers to use any swimming style that they prefer with only a few restrictions.
As defined by the Fédération Internationale de Natation, freestyle swimming allows swimmers to use whatever style they like as long as some part of the swimmer's body breaks the surface during the race. Swimmers may be submerged at the start of the race and after each turn, but only for 15 meters at most, at which time the swimmer's head must break the surface of the water. The rules also stipulate that swimmers must touch the wall at the end of each length and at the finish of the race. Two exceptions for competition are the individual-medley and medley-relay events, in which swimmers are not allowed to use the backstroke, breaststroke or butterfly techniques.
Though swimmers are free to choose any technique they like, the front crawl is most commonly used as it has been demonstrated to be the fastest among elite athletes. Freestyle swimming has been a part of the Olympics since 1896. There are a number of different types of freestyle competition that have swimmers cover different distances, in addition to the medley and relay variants.