The "horse-collar tackle," in which a defender grabs inside the back or side of an opponent’s shoulder pads and pulls that player down, is prohibited.  Named the "Roy Williams Rule" after the Dallas Cowboys defensive back whose horse-collar tackle during the last season caused serious injuries to Philadelphia Eagles wide receiver Terrell Owens, Tennessee Titans wide receiver Tyrone Calico, and Baltimore Ravens running back Musa Smith.
Peel-back blocks (where an offensive player blocks a defender who is moving back toward the direction of his own end zone) below the waist and from the back are now illegal.
Unnecessary roughness would be called for blocks away from the play on punters or kickers, similar to the same protection quarterbacks have after interceptions.
When time is stopped by officials prior to the snap for any reason while time is in, the play clock resumes with the same amount of time that remained on it - with a minimum of 10 seconds. Previously, the play-clock would be reset to 25 seconds.
During field goal and extra point attempts, the defensive team will be penalized for unsportsmanlike conduct if it calls consecutive timeouts in an attempt to "ice" the kicker. Previously, the second timeout request was only denied by officials, and thus could be used to distract the kickers.
Players cannot run, dive into, cut, or throw their bodies against or on an opponent who is out of the play or should not have reasonably anticipated such contact.
If the defensive team commits a dead ball foul following the end of the half, the offensive team may choose to extend the period for one more play. Previously, the half automatically ended without the defensive team being penalized.
During a punt, if the kicking team illegally touches the ball inside the 5-yard line, the receiving team has the option of either treating the result as a touchback or replaying the down with a 5-yard penalty against the kicking team. Previously, the receiving team's only options were either the latter or taking over possession at the spot of the foul. This change prevents an ineligible player from keeping a kick from entering the end zone and becoming a touchback.
If the kicking team commits a penalty, the receiving team can have the option of adding five yards to the return or taking a penalty and forcing the kicking team to rekick the ball. Previously they could take the latter or decline the penalty.
If a team calls for an instant replay challenge after it has used all its challenges or is out of timeouts, it will be assessed an unsportsmanlike conduct penalty. The penalty will also be assessed if a team calls for a challenge inside of two minutes of either half or overtime, when only the replay assistant can initiate reviews. Previously, the request was only denied by the Referee. This change was made to prevent head coaches from constantly stopping the game for any reason, including to just argue with the Referee.
Teams are only able to request an instant replay challenge by tossing their red flag to get the attention of officials. The league decided to do away with the electronic pager/vibrating alert system used by head coaches because practically all of them always used their red flags instead of their pagers anyway. (However, the replay assistant will still use the pagers to notify the officials of a replay request.)