Not every call can be reviewed, and that surprises people. A coach can ask officials to look again at some rulings by throwing a red flag, but only clear, factual ones: was the pass caught, was the player down, did the ball cross the line.
How a challenge works
Every head coach carries a red flag. To challenge a call he throws it onto the field before the next play starts, and officials stop to look at the ruling again on a monitor.
The standard for changing a call is high. There has to be clear evidence the original was wrong. A call that merely looks close on replay stands as it was given on the field.
The rulebook sets out what a coach gets:
NFL rulebook, Rule 15 (Coach Challenges). Each team is permitted a minimum of two challenges that will initiate Instant Replay review… Each challenge requires an available team timeout… A team will be permitted a third challenge if it is successful on at least one of its challenges.
Two things follow from that, and together they keep coaches honest. A challenge is never free, because it costs a timeout if you lose it, and a third one has to be earned by getting one of the first two right. So a coach who hates a call late in a half will sometimes visibly decline to throw the flag: the timeout is worth more to him than the review.
You can also lose a timeout for challenging something that was never challengeable in the first place, which is what happened to Pittsburgh’s Mike Tomlin in 2024 when he threw the flag on a play that could not be challenged at all.
Some things get reviewed whether anyone asks or not. Every scoring play and every turnover is checked automatically. And inside the final two minutes of each half, and in overtime, coaches lose the power to challenge entirely: the replay booth and the league’s command centre in New York take it over.
What can and cannot be reviewed
The whole system runs on one idea: objective, not judgement.
Reviewable is anything with a factual answer. Did the foot land in bounds. Did the knee touch the ground before the ball came loose. Did the ball cross the goal line. Was the pass caught, was the runner down, where exactly should the ball be spotted.
Not reviewable is anything that depends on an official’s opinion, which means very nearly every penalty. Holding, offside, unnecessary roughness, false start, pass interference. Subjective calls stay off the table, and they stay off it even when the replay makes a missed one obvious to everybody watching at home.
There is one well-known exception in the history. In 2019 the league made pass interference reviewable for a single season, after a notorious missed call in a conference championship. The experiment did not work and was dropped after one year. The whole story is on the penalties page.
Since 2025 the booth has been able to fix a narrow set of objective things inside penalties, under the expanded replay assist rules: whether there were too many players on the field, or whether the ball was tipped before an interference call. The judgement at the heart of it, whether a defender actually held or interfered, still belongs to the officials in real time.
The catch that changed the rule
The clearest example of replay doing its job and satisfying nobody came at Lambeau Field on 11 January 2015, Green Bay against Dallas in the playoffs.
Dallas were behind, on fourth down, inside the last five minutes. Tony Romo threw deep to Dez Bryant, who caught it, took two steps and stretched for the goal line. As he landed, the ball touched the ground. On the field it was given as a catch. Green Bay’s Mike McCarthy challenged, and it was overturned to an incomplete pass, because the catch rule of the time required him to hold the ball through his contact with the ground.
Dallas turned it over on downs, Green Bay ran out the clock and won 26-21. By the letter of the rule as it stood, the overturn was correct. It still felt wrong to almost everyone watching, and the catch rule was rewritten years later largely because of plays like it.
That is replay at its most powerful and its most maddening at once: the technology worked exactly as designed, and the rule it was enforcing was the problem.
Common questions
How does a coach’s challenge work?
A head coach throws a red flag before the next play to ask officials to review a call. Each coach gets two challenges a game, and a third only if he wins at least one of them. Every challenge needs an available timeout, and losing one costs that timeout. Inside the last two minutes of each half, and in overtime, coaches cannot challenge and the replay booth handles reviews instead.
Can you challenge a penalty in the NFL?
Mostly no. Judgement calls such as holding and pass interference cannot be challenged, even when a replay makes the mistake obvious. Replay deals with objective questions: whether a pass was caught, whether a runner was down, where the ball should be. Since 2025 the booth can correct a few clear-cut things inside penalties, such as too many players on the field.
Where to go next
- NFL rules decoded: how the whole game fits together
- Penalties and pass interference decoded: the judgement calls replay will not touch
- NFL downs explained: what a turnover on downs actually costs
- Scoring decoded: touchdowns are the most reviewed call in the sport
Replay is Rule 15 of the official NFL rulebook, published by NFL Football Operations, and the Video Rulebook has clips of real reviews.