Title: American football plays
Content:  The offensive team must have seven players on the line of scrimmage at the start of a play. Those players may be positioned at any place along the line of scrimmage (which extends all of the way across the playing field). The defensive team may position as many as 11 players on the line of scrimmage. Usually, there are from 3 to 8 defensive players on the line of scrimmage.
Title: American football rules
Content:  formation, all behind their line of scrimmage (that is, on their side of the ball). For reasons of safety and competitive balance, there are strict rules which define the way in which the offensive players may line up. Seven players must line up directly on the line of scrimmage while four players line up behind the line of scrimmage. Within this formation, there are six eligible receivers who may receive a forward pass during play. These eligible receivers are either the running back, fullback, tight end, or wide receivers. The remaining five linemen, often called interior linemen do not normally handle the ball during a play. 
Title: Canadian football
Content:  from sideline to sideline for the length of the ball) is referred to as the line of scrimmage. This line is similar to "no-man's land"; players must stay on their respective sides of this line until the play has begun again. For a scrimmage to be valid the team in possession of the football must have seven players, excluding the quarterback, within one yard of the line of scrimmage. The defending team must stay a yard or more back from the line of scrimmage. On the field at the beginning of a play are two teams of 12 (and not 11 as in American football). The team 
Title: Line of scrimmage
Content: Only the offensive player who snaps the ball (usually the center or long snapper) is allowed to have any part of his body in the neutral zone. ; For there to be a legal beginning of a play, at least seven players on the offensive team, including two eligible receivers, must be at, on, or within a few inches of their line of scrimmage. ; Beginning in 2019, high school football will allow as few as five players on a line of scrimmage, but in practice, the limits will remain the same since teams will still be limited to four persons behind the line of scrimmage; the difference would only come into play if a team plays offense with fewer than 11 players. 
Title: Line of scrimmage
Content:  A line of scrimmage is parallel to the goal lines and touches one edge of the ball where it sits on the ground prior to the snap. In American football, the set distance of the line of scrimmage between the offense and defense is 11 in, the length of the ball. In Canadian football, the set distance of the line of scrimmage is 1 yd, more than three times as long as the American line. Under NCAA, and NFHS rules, there are two lines of scrimmage at the outset of each play: one that restricts the offense and one that restricts the defense. The area between the two lines (representing the length of the ball as extended to both sidelines) is called the neutral zone.
Title: American football positions
Content:  Four backs line up behind the line of scrimmage. Additionally, there are two receivers, one on each end of the line of scrimmage, who line up outside of the interior linemen. There are four main positions in this set of players:
Title: List of gridiron football rules
Content:  Before scrimmage, an official places the ball at the spot it became dead, but no nearer than 24 yd from the sideline or 1 yd from the goal line. The line parallel to the goal line passing through the ball (line from sideline to sideline for the length of the ball) is referred to as the line of scrimmage. This line is a sort of "no-man's land"; players must stay on their respective sides of this line until the play has begun again. For a scrimmage to be valid the team in possession of the football must have seven players, excluding the quarterback, within one yard of the line of scrimmage. The defending team must stay a yard or more back from the line of scrimmage.
Title: Starting lineup
Content:  In American football since the 1950s, most upper level teams use a three-platoon system, each with its own starting lineup. The starting lineups for offense and defense, each with eleven players, typically get the most attention. The starting lineups are defined as the eleven players who take the first offensive or defensive play from scrimmage of a given game. (An offensive player does not have to be on the team that gets possession first to be considered a starter, nor does a defensive player have to be on the team that does not; the first play from scrimmage after the first change of possession counts as well.) The third platoon, special teams, in modern times is composed mostly of backup and reserve players from the offensive or defensive platoons, with the exception of the placekicker or punter; the players who, for instance, take part in the opening kickoff are typically not considered starters. The player positions dictate certain responsibilities and privileges in regard to handling the ball. A uniform numbering system restricts players' ability to change positions in the middle of the game.
Title: Offensive backfield
Content:  There are many rules which differ for play in the offensive backfield as opposed to play in front of the line of scrimmage. The 1906 football rule reforms mandated that the offensive team line up with at least seven players on the line of scrimmage, which are now commonly called "linemen". Therefore, a maximum of four players are allowed in the offensive backfield. The other players not on the line of scrimmage may be positioned anywhere, but all must be at least 1 yard behind the seven or more players on the line of scrimmage. A forward pass can only be legally made from the offensive backfield. There are also rules If the 
Title: List of formations in American football
Content:  The following is a list of common and historically significant formations in American football. In football, the formation describes how the players in a team are positioned on the field. Many variations are possible on both sides of the ball, depending on the strategy being employed. On offense, the formation must include at least seven players on the line of scrimmage, including a center to start the play by snapping the ball. There are no restrictions on the arrangement of defensive players, and, as such, the number of defensive players on the line of scrimmage varies by formation.

Question: how many players on the line of scrimmage in american football?
Answer: at least seven players.
at least seven.
seven.