American football grew out of rugby and soccer, two older sports, and its first college game, played between Rutgers and Princeton on November 6, 1869, used modified London Football Association rules. You may have heard that football has always been played with the same rules, but the history says otherwise. 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.

The professional game has its own early history. William (Pudge) Heffelfinger was paid $500 to play in a football game for the Allegheny Athletic Association, but proof that he was paid did not become public for almost 80 years, until the Pro Football Hall of Fame displayed an expense sheet. The Pro Football Hall of Fame says that research after it opened in 1963 uncovered the Pudge Heffelfinger payment by the Allegheny Athletic Association in 1892 and negated the Latrobe claim as the birthplace of pro football. 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.

A football is not round, and it is covered in tan leather. Each football team has 11 players on the field at one time, and as of November 2026, an NFL field is a rectangle 360 feet long and 160 feet wide. A team scores a touchdown by getting the ball across the other team's goal line, and a touchdown is worth six points. 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.

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. 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. A fumble happens when a player with the ball loses it, and either team can recover it.

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. Football players wear helmets that have a face mask, and in the NFL a player's jersey number shows what position he plays. The NFL put players' names on the backs of their jerseys and made the scoreboard clock the official timer, and goal posts offset from the goal line, painted bright yellow, became standard in the NFL.

Helmets tell much of the story of the rulebook. 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.

Kicking has its own rules. 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 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. 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.

Overtime shows how the rules keep moving. 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, NFL regular-season overtime for 2026 is a single 10-minute period in which both teams get a chance to possess the ball, and in college overtime, starting with the third extra period, each possession is a single two-point try from the three-yard line. As of November 2026, the NFL rulebook for 2026 lets the kicking team declare an onside kick at any time during the game, and as of November 2026, in college football in 2026, coaches receive two replay challenges and a third if either is successful.

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. The International Federation of American Football was formed in 1998, and as of November 2026, USA Football is the sole U.S. member of the International Federation of American Football, the sport's international governing body. As of November 2026, the NFL's 2026 international schedule has nine games at eight venues in seven countries across four continents, and USA Football has begun a talent search for flag football players for the 2028 Olympics.

Words to know

• scrimmage: starting line
• targeting: aimed contact
• overtime: extra play
• merge: join together
• federation: joined groups