A computerized system for calling balls and strikes is undergoing testing during Major League Baseball spring training exhibition games, following four years of trials in the minor leagues. The Automated Ball-Strike System (ABS) is supported by Baseball Commissioner Rob Manfred and could potentially assist MLB home plate umpires as early as 2026 without replacing them.
The ABS technology involves outfitting stadiums with cameras that track each pitch to determine if it crosses home plate within the strike zone. Umpires wear ear buds to receive 'ball' or 'strike' calls, which are then relayed to players and fans using traditional hand signals.
During spring training, human umpires will make the original call on each pitch, but teams will have the opportunity to challenge two calls per game. Challenges must be made within 2 seconds by the batter, pitcher, or catcher tapping their helmet or cap. The umpire then announces the updated count after reviewing the pitch and strike zone graphic displayed on the scoreboard and broadcast feed.
MLB has installed the ABS system in 13 spring training ballparks hosting 19 teams across Florida and Arizona. The technology uses a Hawk-Eye pose-tracking system with cameras to track pitches and determine if they fall within the rectangular ABS strike zone.
ABS testing began in the independent Atlantic League in 2019 and progressed through the minor leagues, with a challenge system introduced in 2021. The system was expanded to Triple-A stadiums in 2023 and fully implemented in 2024.
Teams had a 51% success rate with challenges in Triple-A last season, with defense challenges winning 54% and offense challenges winning 48%. The ABS strike zone has evolved in width and height over time, impacting walk and strikeout rates.
Concerns about broadcasts potentially influencing challenges led MLB to consider various alternatives, such as showing the strike zone box without the ball or vice versa. Players can provide feedback on the ABS system using a dedicated application on dugout iPads.
