MLB swinging for the fences with automated pitch-review system

Major League Baseball will implement automated ball and strike technology in 2026 following approval by the league’s 11-member competition committee [1]. The Automated Ball/Strike System (ABS) will operate as a challenge-based format where human umpires continue making initial calls, but teams can contest those decisions using computer verification [2].

How the ABS system works

Core technology:

The ABS uses 12 Hawk-Eye cameras installed around the stadium and connected by T-Mobile’s private 5G network to track the location and trajectory of every pitch [3]. The strike zone is precisely defined for each batter based on individual height, measured independently before each game [4]. The zone is typically set at 53.5% of batter height for the top and 27% for the bottom, creating a two-dimensional area aligned with the width of the plate [4].

Challenge process:

Only the pitcher, catcher or batter may initiate a challenge by tapping their hat or helmet [4]. The umpire announces the challenge, and nearly instantaneously, a digital graphic shows the pitch’s position relative to the strike zone on stadium scoreboards and TV broadcasts [3]. Teams get two challenges per game, plus one per extra inning if needed, and retain challenges when the ABS overturns the umpire’s call [5].

The review procedure takes approximately 15 seconds, making it one of MLB’s fastest replay technologies [6]. If any part of the ball touches any edge of the strike zone rectangle, the pitch is classified as a strike [3].

The human umpire’s evolving role

Human umpires will continue to call every pitch initially using traditional hand signals and perform all other duties on the field — positioning, rules enforcement, ejection protocols and managing safe/out calls [7]. The ABS is only triggered when a player challenges a specific call, so for most pitches, the umpire’s judgment remains final [7].

When a challenge occurs, umpires facilitate the process, communicating the appeal and displaying the ABS ruling to players, fans and broadcasters [8].

Impact on game dynamics

The digital review adds about 15 seconds per challenged pitch. During testing, games averaged around 4 challenges per game with over 50% success, meaning fewer than 2% of pitches were challenged [4][6]. This minimal usage ensures limited delays to game flow.

Catcher “framing” (subtly positioning a pitch to influence the umpire’s call) will be less effective, as challenged pitches are objectively reviewed by ABS [10]. The emotional and strategic elements of arguing ball/strike calls will be diminished, as factual review replaces subjective debate in disputed situations [10].

Implementing automated challenges is projected to reduce on-field ejections, as over 60% of recent MLB ejections were related to ball/strike disputes [5]. Since ABS makes appealed calls final and publicly displays digital results, there is less incentive for prolonged disputes regarding strike zone decisions [5].

Testing history and results

The ABS system was first piloted in the Atlantic League and Arizona Fall League in 2019, followed by extensive trials at the Triple-A level [12]. More recent trials included 13 spring training ballparks and all regular-season Triple-A games using the challenge format [4].

ABS was used for official challenge at the 2025 MLB All-Star Game in Atlanta, with 4 out of 5 disputed calls overturned by the system [13]. Players, coaches and umpires overwhelmingly preferred the challenge system over a fully automated version, citing improved engagement and strategy [12].

Stadium implementation

Every MLB stadium will be outfitted with 12 Hawk-Eye cameras to cover all pitch angles and home plate, using triangulation and advanced tracking algorithms for precise measurements [14]. All camera data are transmitted via T-Mobile’s 5G Advanced Network Solutions to enable nearly real-time reviews, graphics and in-stadium screens for fans [3].

Future oversight and accountability

The system shifts umpire oversight procedures since ball and strike disputes — historically a top driver of ejections — are now subject to review and appeal. Disciplinary and rating mechanisms for umpires focus more on non-ball/strike decisions and professionalism, as strike zone accountability shifts toward Hawk-Eye’s objective tracking [15].

ABS rulings are immediate and final for challenged pitches, outsourcing accuracy oversight for those calls to the technology [16]. Future discipline and oversight will focus on enforcing proper ABS process rather than subjective plate judgments [3].

Sources

[1] https://www.mlb.com/news/abs-challenge-system-mlb-2026

[2] https://www.espn.com/mlb/story/_/id/46357017/mlb-approves-robot-umpires-2026-part-challenge-system

[3] https://www.mlb.com/news/press-release-mlb-announces-abs-challenge-system-coming-to-the-major-leagues-beginning-in-the-2026-season

[4] https://www.espn.com/mlb/story/_/id/46357017/mlb-approves-robot-umpires-2026-part-challenge-system

[5] https://www.nbcnews.com/sports/mlb/robot-umpires-mlb-balls-and-strikes-rcna233274

[6] https://www.si.com/mlb/baseball-new-abs-challenge-system-numbers-suggest-one-position-crucial

[7] https://6abc.com/post/robot-umpires-approved-mlb-2026-part-challenge-system/17871759/

[8] https://www.foxsports.com/stories/mlb/robot-umpires-coming-mlb-heres-how-work

[10] https://sportsanalytics.studentorg.berkeley.edu/articles/backwards-k.html

[12] https://www.baseballamerica.com/stories/11-things-to-know-about-mlbs-new-abs-challenge-system-for-2026/

[13] https://apnews.com/article/mlb-robot-umpires-allstar-game-5aabcdcd07eb9070060308edff858615

[14] https://www.theverge.com/news/783982/mlb-baseball-robot-umpires-abs

[15] https://www.cbssports.com/mlb/news/mlb-robot-umpires-automated-ball-strike-system-approved-2026-season/

[16] https://www.nytimes.com/athletic/6655235/2025/09/23/mlb-automated-ball-strike-robot-umps/