Offside (American football)

Offside is a minor foul in gridiron football caused when a player crosses the line of scrimmage ahead of the snap of the ball.

In gridiron football, offside is a foul in which a player is on the wrong side of the line of scrimmage when the ball is snapped.

[1] In high school games played under the NFHS ruleset, the term "offside" is not used; rather the foul is referred to as encroachment and causes the ball to remain dead.

Prior to 1925, a call of offside against a defensive unit brought with it an automatic first down in addition to a five-yard advancement of the ball for the offense.

[2] However, a December 1924 meeting of the Football Coaches' Association of America spurred a change of rules for the 1925 season eliminating the provision for an automatic first down, while leaving the five yard penalty intact.

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