A variant of the corner route in football that requires the receiver to run up the field perpendicular to the line of scrimmage and turn roughly 45 degrees in the direction of the sidelines.
Longer corner routes such as the flag route aim for large gains or the end zone, and are usually more effective when receiver is in isolated coverage, with the defensive back playing inside.
The corner route is often discussed or paired with the post route, which mirrors the corner but heads toward the center of the field rather than toward the sideline. Because the initial vertical dash of both routes are basically the same, wide receivers running corners can fake running the post, when in actuality they are planning to turn toward the corner. The corner and post routes will often both be used in the same play, in an effort to split the defense, and the post-corner route combines both post and corner movements in its execution.
Also sometimes referred to as the “flag corner.”