Chiefly because there is no dominant sanctioning organization for the sport, the game has mutated into many variations: 9-man, 8-man, 7-man, 5-man, and 4-man on a side; with kicking and punting and without; with point-after conversions (including some with 1, 2, and 3 point tries) or without; and field sizes that vary from full CFL size, NFL size (120 yards long by 53 1/3 yards wide), to fields a third that size.

An important distinction is whether linemen are allowed to catch passes ("Eligible Linemen") or, as in the CFL / NFL, are not allowed to do so ("Ineligible Linemen"). Flag (and touch) football may also be divided into "contact" or "non-contact", depending on whether or not blocking is allowed; if allowed, blocking is usually restricted to the chest.

In Non-Contact flag football, there is no blocking, usually no linemen, and if there are linemen they can not use their hands to block an opponent. Defensive players cannot get in the way of a runner; they can only attempt to grab the flag without impeding the path of the runner. Offensive players are not allowed to hand block defensive players to prevent them from grabbing the flag.

In Contact flag football, none of the rules above apply. There are linemen blocking only around chest area, no chop blocks or blocks below the waist. Defensive players can get in the path of an offensive player to attempt to grab the flag. Offensive players can hand block defensive players attempting to grab the flag.

Organized flag football leagues follow a number of sets of rules, with variants including:

The sport has a strong amateur following and several national and international competitions each year sponsored by various associations.

The International Flag Football Federation sponsored World Cup of Flag Football featuring teams from the United States, Mexico and several other nations.

The International Woman's Flag Football Association hosts contact flag football tournaments across the world with participants from the United States, Canada, Mexico, Sweden, Norway, Finland, Denmark and several other nations. The organization also known as the IWFFA is the largest organization for women and girls in the sport of flag football. The most active tournament is held each February in Key West, Florida, called the Kelly McGillis Classic where over 30 women and girls teams participate in 8on8 contact flag football.

In Korea, the biggest tournament is the National Flag Football Tournament held by the Korean Flag Football Federation (KFFF). It attracts up to 20 teams, from middle school students to adults.

The United States Flag and Touch Football League (USFTL) has a number of smaller organizations spread out over the US. Located in Ohio, this league supports a number of teams from the Mid Atlantic, NorthEast, and Midwest states.