Uniform number (American football)

Uniform numbers in American football are unusual compared to those in other sports. They are displayed in more locations on the uniform; they are universally worn on both the front and back of the jersey; and in many cases "TV numbers" are displayed on either the jersey sleeves, the shoulder pad, or occasionally on the helmets. The numbers on the front and back of the jersey also are very large, covering most of the jersey. More important, certain numbers may only be worn by players playing specific positions; thus, the jersey numbers assist the officials in determining possible rules infractions by players.

Under current rules in all three of the most prominent levels of American football (high school football, college football and professional football), all players must wear a number between 1 and 99, and no two players may wear the same number on the field at the same time. In the past, players have used the numbers 0, 00 and in two special cases 100. (0 and 00 are still allowed and used in Canadian football.) Those who wear numbers between 50 and 79 are, by rule, prohibited from catching or touching forward passes if their team is in possession of the ball, unless explicitly indicated to the referee during a Tackle-eligible play. Other than this, the correspondence between jersey numbers and player positions is largely an issue of semantics.

The National Football League numbering system dates from a large scale change of their rules in 1973, subsequently amended in various minor ways. As of 2015, players are generally required to wear numbers within ranges based on their positions as shown in the following table.

Long snappers, not listed in the league's numbering system, can wear any number from 40 to 99; as the long snapper is seldom listed as a distinct position, players who long-snap are often listed as backup centers or backup tight ends.

...
Wikipedia