Offside (American football)

For offside rules in other sports, see Offside (sport).
All players from both teams must stay on their side of the line of scrimmage until the point of the snap to avoid committing an offside penalty. Only the ball snapper, in this case the center, can be in the neutral zone but otherwise cannot advance beyond it. In this picture, the line of scrimmage happens to line up with the horizontal white-painted 10-yard line

Offside is a minor foul in gridiron football caused when a player crosses the line of scrimmage ahead of the snap of the ball. The penalty associated with the infraction is the advancing of the ball five yards and a replay of the down.