Indoor, also known as Arena Football was developed in the 1980s. It is played on a 50 yard field and there are five downs to score. There are 8 players on the field per team at any one time.
Variations on 8-a-side Football include the Legends Football League (7-a-side Womens), American 7s (Unkitted Tackle Football) and 8-Man Football, played outdoors in smaller locations.
Arena Football Leagues: