While Overwatch is played in teams of five, Overwatch League teams can have up to six additional players that can be swapped between maps. A team's membership is locked at the start of the season, but a mid-season signing period allows teams to bring in new players or trade players between teams. Following the end of the season, teams have about one month to extend current player contracts, bring on players from affiliated Overwatch Contenders teams, or hold private tryout sessions. Subsequently, all unsigned players by the end of this period enter free agency during which players can negotiate with teams to become part of the roster; in the case of when expansion teams are added, there is a month-long period where expansion teams have exclusive negotiating rights before other teams can engage. A team's minimum roster is to be set prior to the season's pre-season matches, about two months prior to season play, but they can expand and change this roster up until a specified date. The league is not region-locked, so teams can use players of any nationality to fill their ranks, as long as the team ownership is based in that city or region. For example, the London Spitfire at the onset of the first season was entirely made up of South Korean players. The only restriction on players is to be of at least 17 years old and to be able to travel internationally.
