term. According to the official International Tennis Federation
) rules (as found on USTA
A player (the server) commits a foot fault if after his feet are at rest but before he strikes the ball, either foot touches:
The rules also state that a player must actually make an effort to hit the ball for a foot fault to occur. In other words, if a player's feet
are placed illegally (as described above), but does not swing at the ball, it is not a foot fault.
A foot fault carries the same weight as any other fault (such as serving the ball into the net). Two consecutive faults of any type result in a double fault.
Foot faults are rather rare in professional tennis.