MLB approves Automated Ball/Strike System for 2026, keeping human umpires on the field

That decision comes after years of testing and refinement. The Automated Ball/Strike System, known as ABS, has been trialed in the minors since 2019. The independent Atlantic League staged a run in 2019, and MLB installed the technology that year in the Arizona Fall League. The Low-A Southeast League used eight of its nine ballparks in 2021, before moving ABS up to Triple-A in 2022. At the start of the 2023 season, Triple-A split its games between those using ABS for balls and strikes and those managed by humans subject to appeals. MLB then shifted Triple-A to an all-challenge system on June 26, 2024, and this year tested the format at 13 spring training ballparks hosting 19 teams in 288 exhibition games. Teams won 52.2 percent of their ball/strike challenges (617 of 1,182). In Triple-A this season, the average challenges per game rose to 4.2 from 3.9, while the success rate dipped to 49.5 percent from 50.6 percent. Defenses won 53.7 percent of challenges and offenses 45 percent.

In the big-league All-Star Game test, four of five ABS challenges on plate calls by umpire Dan Iassogna were successful. Triple-A rules do not grant extra challenges in extra innings. The Tuesday proposal includes a provision granting teams one additional challenge per inning if they have exhausted their allocated challenges. MLB has experimented with different strike-zone interpretations for ABS, including three-dimensional versions. Current practice calls strikes based on where the ball crosses the plate’s midpoint, with the system using an 8.5-inch depth from front to back and a strike-zone top at about 53.5 percent of a batter’s height and the bottom at 27 percent.

"Throughout this process we have worked on deploying the system in a way that's acceptable to players," Commissioner Rob Manfred said in a statement. "The strong preference from players for the challenge format over using the technology to call every pitch was a key factor in determining the system we are announcing today."

This will be MLB's first major rule change since 2024, which included a pitch clock, limitations on defensive shifts, restrictions on pitcher disengagements such as pickoff attempts, and larger bases. The new challenge format is designed to preserve pitch framing as a strategic element for catchers, while introducing a verified system to adjudicate borderline pitches.

Umpire representative Bill Miller is part of the process that guides how ABS is implemented across the 30 clubs. The union’s decisions reflect input from players across the league, and the competition committee, which also included players such as Austin Slater and others, weighed both the potential accuracy gains and the impact on game flow.

Reaction from club officials and players reflected a mix of cautious optimism and realism. Yankees manager Aaron Boone called the adoption "inevitable" and noted that while he has been tentative about the exact implementation, he expects positive outcomes if used thoughtfully. "Throughout the year, I've been a little not totally on board with it or exactly how it's going to be implemented but it's going to be here and hopefully that's a good thing," Boone said. "A lot of the things that Major League Baseball has done I think have been really successful in the changes they've made and hopefully this is another one of them." Cleveland Guardians manager Stephen Vogt said players will have to adapt, adding, "You can like it, dislike it, it doesn't matter. It's coming. It's going to change the game. It's going to change the game forever."

Other managers weighed in, including St. Louis Cardinals skipper Oliver Marmol, who noted the ABS system, built on Hawk-Eye tracking, has roots in the minors and will push the sport to new boundaries of officiating. MLB has emphasized that ABS is designed to augment, not replace, human judgment, maintaining the value of umpire calls while offering a transparent, reviewable process for disputed pitches.

The announcement marks a significant milestone in baseball's ongoing embrace of technology. It follows a broader run of innovations that began with a pitch clock and evolved through changes meant to speed up play and standardize officiating. While the system will still rely on on-field umpires for final calls, the ability to challenge and the public display of reviews on videoboards will introduce a new dynamic to the strike zone and how players approach plate discipline.

As MLB moves toward a 2026 rollout, teams, players and fans will watch closely to see how ABS affects game pace, strike-zone interpretation, and ejection rates. MLB noted that last year’s data showed a majority of balls and strikes were correctly called, but the challenge format is intended to provide a corrective mechanism for especially borderline calls and to reduce the number of prolonged disputes that generate ejections. The league also framed ABS as part of a measured approach to integrating technology in a way that respects the human element of the game while delivering more consistent outcomes.