Robot umpires are coming to MLB. Here's how they work

The ABS system, powered by Hawk-Eye, has seen years of rigorous testing in minor league play. The independent Atlantic League famously trialed the technology at their 2019 All-Star Game, prompting MLB to incorporate it into that year’s Arizona Fall League. The program continued to expand, covering eight out of nine ballparks in the Low-A Southeast League in 2021. Following these successful pilots, the technology officially moved up to the Triple-A level in 2022, providing a much larger sample size for evaluation.

At the beginning of the 2023 season, Triple-A games split testing duties, with half using the automated system exclusively and others allowing teams to appeal calls to the machine. MLB eventually transitioned Triple-A to the full challenge system on June 26, 2024. This model was subsequently deployed across 13 spring training sites, hosting 19 teams and 288 exhibition games. The results were telling, as teams successfully overturned 52.2% of their ball-strike challenges. Furthermore, during last year's All-Star Game, four out of five challenges against the umpire proved successful.