Football's rulebook has a long history. American football grew out of rugby and soccer, two older sports, and the first college football game was played between Rutgers and Princeton on November 6, 1869, under modified London Football Association rules. The first Harvard-Yale game was played on November 13, 1875, and at the Massasoit convention in 1876, the first rules for American football were written. Walter Camp, who played at Yale, became known as the father of American football, and he invented the line of scrimmage and the system of downs. The flying wedge, football's major offense in 1905, spurred the formation of the NCAA, which grew out of a 1905 meeting of colleges that wanted to reform football's playing rules, and President Theodore Roosevelt summoned athletic leaders to White House conferences to urge reform of football.

A football is not round, and it is covered in tan leather. Each football team has 11 players on the field at one time. A team scores a touchdown by getting the ball across the other team's goal line, and a touchdown is worth six points, although in 1892 a touchdown counted four points and a touchdown used to be worth five points before it was increased to six. After a touchdown, a team can try to score one or two more points, while a field goal is worth three points and a safety is worth two points. The team with the ball gets four downs, or tries, to move the ball 10 yards. As of November 2026, a 40-second play clock starts when a play ends, and the team that does not snap the ball in time gets a five-yard penalty. The neutral zone is the space between the two teams' lines before the snap, and neither team may enter it until the ball is snapped. A player is offside when part of his body is in the neutral zone before the ball is put in play.

As of November 2026, an NFL field is a rectangle 360 feet long and 160 feet wide, and each team puts 11 players on it. Football players wear helmets that have a face mask, and in the NFL a player's jersey number shows what position he plays. The center snaps the ball between his legs to the quarterback to start each play, and the quarterback leads the offense: he tells his teammates which plays to run. A running back is the main ball carrier, and he can run with the ball or catch a forward pass. Wide receivers line up near the sidelines, run downfield and catch passes from the quarterback. A forward pass is thrown by an offensive player, usually the quarterback, from behind the line of scrimmage toward an eligible receiver. A fumble happens when a player with the ball loses it, and either team can recover it.

A punt is a kick in which the kicker drops the ball and kicks it before it hits the ground. A kickoff starts each half and follows each touchdown try or successful field goal, and as of November 2026, the kicking team kicks from its own 35-yard line on a kickoff. The NFL moved goal posts from the goal line back to the end lines and moved kickoffs from the 40- to the 35-yard line, and NFL owners voted to move kickoffs from the 30-yard line to the 35-yard line. NFL clubs adopted kickoff changes, including a ban on wedge blocks. NFL safety rules banned blocking below the waist by the receiving team on kickoffs, punts and field-goal attempts, and told officials to blow the play dead quickly when a quarterback was clearly in a tackler's grasp.

Helmets tell much of the story. You may have heard that players have always worn helmets, but the NFL made wearing helmets mandatory, and it prohibited plastic helmets. The NFL added a 15-yard penalty for roughing the passer, and it ruled the ball dead immediately if a ball carrier in the grasp of an opponent touched the ground with any part of his body except his hands or feet. The NFL put greater restrictions on contact to the head, neck and face. It standardized and expanded protection for defenseless players, and play stops if a ball carrier's helmet is removed. NFL clubs voted unanimously to remove the hip-drop tackle from the game. For the 2024 season the NFL and its players' union introduced five new helmets that achieved record-high testing results. The NCAA football rules committees embrace the targeting rule to promote player safety, reduce head contact and eliminate specific targeting actions from the game, and as of November 2026, the NCAA's definition of the crown of the helmet was approved starting with the 2022 season and focuses on the top of the helmet.

A football game lasts 60 minutes, divided into four quarters of 15 minutes each, and at halftime, between the second and third quarters, play stops and the teams leave the field. Overtime has changed too. The NFL provided for sudden-death overtime in a playoff game that was tied after four quarters, and the first sudden-death overtime in an NFL Championship Game ended with Baltimore beating the Giants 23-17. The NFL installed a modified sudden-death overtime for the 2010 postseason and expanded it in 2012 to cover all NFL games, regular-season and preseason too. In 2022 the NFL expanded postseason overtime so that each team has the opportunity to possess the ball. As of November 2026, in college overtime, starting with the third extra period, each possession is a single two-point try from the three-yard line.

The pro game grew apart from the college one. William (Pudge) Heffelfinger was paid $500 to play in a football game for the Allegheny Athletic Association. A league of pro teams changed its name to the American Professional Football Association, and the American Professional Football Association changed its name to the National Football League. The NFL, which long had followed the rules of college football, made a number of significant changes from the college game for the first time. In 1966 the NFL and the American Football League agreed to merge and to play an annual contest between their champions in the meantime. Lamar Hunt, who owned the Kansas City Chiefs, suggested the name Super Bowl, inspired by a bouncy toy called the Super Ball. The first Super Bowl was won by the Green Bay Packers over the Kansas City Chiefs, who were champions of the rival AFL. The Pro Football Hall of Fame was dedicated at Canton, Ohio, on September 7, 1963.

Words to know

• scrimmage: starting line
• targeting: aimed contact
• offside: too far forward
• overtime: extra play
• wedge: tight group