In September 2025 Major League Baseball’s Joint Competition Committee approved the Automated Ball-Strike (ABS) Challenge System for the 2026 season, after testing it across 2025 spring training. Rather than letting a computer call every pitch, MLB chose a challenge model: a human umpire still calls balls and strikes, and the batter, pitcher, or catcher may immediately contest a call by tapping their cap or helmet.
The ball is tracked by Hawk-Eye’s optical system, the same technology behind Statcast, and the strike zone is defined geometrically: 17 inches wide like home plate, with the top set at 53.5 percent and the bottom at 27 percent of each player’s measured height, evaluated as a two-dimensional plane over the middle of the plate. Each team starts a game with two challenges and keeps any it wins, losing only those it gets wrong.
The spring-training trial that justified the decision was substantial. Across 288 games teams averaged about 4.1 challenges per game, each taking roughly 13.8 seconds, with an overall overturn rate of 52.2 percent and broad fan approval. The challenge design preserves the human umpire’s authority while using the machine as a precise tiebreaker - a deliberately conservative path to automation in a tradition-bound sport.