Like HowStuffWorks on Facebook!

How American Football Works

Football Instant Replay

In a modern NFL game, there are as many as 20 cameras covering the fast-paced action of a game. In 1999, the NFL added an instant replay system to back up the officials. Each game camera catches a different view of each play, and those views can be used to review questionable calls. However, not every play is reviewable.

During certain plays, coaches can challenge an official's call. The coach challenges the play by tossing a red flag on the field. Each team is allotted two challenges per game. If the team loses the challenge, it loses a time-out and the official's call stands, according to NFL rules. If a team wins the challenge, it retains its time-out and the official's call is overruled. A challenge must be made before the next play begins but cannot occur in the last two minutes of each half.

An official replay assistant can also initiate a review in the last two minutes of each half and in the overtime period. The replay assistant is not limited as to how many replays he can request.

When a play is challenged, the referee has 90 seconds to review the play. He reviews the play at a field-level monitor to the side of the field.

Here is a list of some reviewable plays:

  • Scoring plays
  • Pass complete, incomplete, or intercepted
  • Out of bounds
  • Recovery of a loose ball

    Philadelphia Eagles defense on a loose ball
    Photo courtesy The Philadelphia Eagles
    There's a loose ball in there somewhere.

  • Illegal passes - illegal receiver or beyond line of scrimmage
  • Quarterback incomplete forward pass or fumble
  • Runner rule down by contact
  • Touching of a kick
  • Number of players on the field
Officials are not always 100 percent correct, but their well-trained eyes allow them to be correct the majority of the time.

To learn more about American football, as well as other sports, check out the links on the next page.