How it works
Because the offense controls the snap count, the play is stopped immediately rather than allowed to continue. The NFL penalty is five yards, and the down is replayed.
What people often miss
A false start is different from defensive offside, which involves a defender crossing the line of scrimmage. Officials judge whether an offensive movement was sudden or otherwise simulated the beginning of the play.
Why this question comes up
Crowd noise and changing snap counts make false starts especially visible in road games.
Key points
- A false start occurs when an offensive player makes a prohibited movement that simulates the start of the play before the snap.
- Because the offense controls the snap count, the play is stopped immediately rather than allowed to continue. The NFL penalty is five yards, and the down is replayed.
- A false start is different from defensive offside, which involves a defender crossing the line of scrimmage. Officials judge whether an offensive movement was sudden or otherwise simulated the beginning of the play.
Bottom line
A false start occurs when an offensive player makes a prohibited movement that simulates the start of the play before the snap.
Source and verification
This Answer was checked against NFL Rulebook. Follow the source for the full official explanation and any later updates.