There is no offside at the U8 level, according to the USYS regulations for small-sided soccer. That means that all players are required to be on the field at all times. At the youth age levels below U15, the offside rule is implemented primarily using electronic assistance. The referee has the ability to call an offside if he/she believes it is necessary. At the higher age levels, the offside rule is mainly determined by human interpretation. That is, referees will often ask for advice from other officials or coaches before making a decision on whether or not to call something as simple as a free kick or penalty kick. It's important to remember that the offside rule is there to prevent goals. If a player is offside they should not be in a position to receive the ball. If they are, then the opponent should not be allowed to play them the ball. In general, if a player appears to be in a position where they could possibly receive a pass but isn't directly involved in the play, they're considered offside. Players who are closer to their own goal line than the opposing team's first defender are considered offside.