If you've caught a baseball game recently and noticed a hitter, catcher, or pitcher tapping their helmet after a close pitch, you're witnessing MLB's ABS challenge system in action.
ABS, or Automated Ball-Strike system, isn't about replacing umpires with robots. Instead, it complements the human element by allowing players to challenge ball-or-strike calls when they disagree with the umpire's decision.
Launched for the 2026 season after thorough testing in the minors and spring training, the ABS challenge system is like a quick review tool for the strike zone. Here's how it works: the umpire makes the initial call, and if a player-be it the pitcher, catcher, or batter-disagrees, they can challenge it on the spot. The system checks the pitch's location against the batter's strike zone and confirms or overturns the call, with results shown on the ballpark videoboard and TV broadcast almost instantly.
This system isn't about eliminating umpires but rather enhancing their calls with technology for those crucial moments. Players, not managers or coaches, have the power to challenge, and they must do so immediately, usually within about two seconds, by tapping their helmet or cap.
Each team starts with two challenges per game. If a challenge is successful, the team keeps it.
If not, it's gone. This setup adds a strategic layer, as players must decide if a close call is worth one of their limited challenges.
In extra innings, if a team has no challenges left, they receive one. But if they still have one, they don't get an extra. Some restrictions apply: challenges aren't allowed when a position player pitches or after replay reviews.
The strike zone used by ABS is standardized and personalized. It’s a two-dimensional plane at the middle of home plate, 17 inches wide.
The top and bottom are set at specific percentages of the hitter's height. If any part of the ball touches this zone, it's a strike.
This precise measurement might differ slightly from the TV graphic strike zone, as ABS uses Hawk-Eye technology with 12 cameras tracking each pitch to an accuracy of about one-sixth of an inch.
Does this slow the game down? Not really.
During 2025 spring training, there were an average of 4.1 challenges per game, each taking about 13.8 seconds. That's less than a minute of added time per game, and the number of pitches per plate appearance remained steady.
In essence, the ABS system isn't about re-calling every pitch but offering players a chance to correct significant misses without sidelining the umpire. So, next time you see a quick helmet tap, know that it's baseball's modern way of saying, "Let's double-check that call."