Robot umpires are now part of Major League Baseball, but they do not call the game. Starting in 2026, MLB uses the Automated Ball Strike (ABS) challenge system: the home plate umpire still calls every pitch, and the batter, pitcher or catcher can challenge a ball or strike call, which is then checked against a tracking camera strike zone in seconds. Each team starts a game with two challenges and keeps any challenge it wins. About half of all challenges have been overturned.
How the ABS Challenge System Works
| Rule | How it works in 2026 |
|---|---|
| Who can challenge | Only the batter, pitcher or catcher; managers cannot |
| Challenges per team | Two to start the game; a successful challenge is kept |
| When you lose them | After two unsuccessful challenges |
| Extra innings | Each team gets a challenge to start every extra inning |
| Strike zone | 17 inches wide at the middle of the plate; top at 53.5% and bottom at 27% of the batter’s height |
| Technology | Hawk-Eye tracking cameras on a private 5G network |
| Who calls pitches | The home plate umpire still calls every pitch |
To challenge, the player signals right after the call, and the pitch appears on the ballpark video board with the automated zone so everyone can see the result. The system was approved by MLB’s Joint Competition Committee and is used in spring training, the regular season and the postseason. A handful of special event games held outside MLB ballparks, such as the Field of Dreams game, do not have the equipment and play without it.
How Often Calls Are Overturned
Players challenged a little more than four pitches per game in testing, and the success rate has stayed near 50 percent. Through early September of the 2026 season, players had made nearly 9,000 challenges with an overturn rate of about 54 percent. Catchers were the most successful challengers in testing, while batters challenge most often with two strikes and in full counts, when a single call can end an at bat. The live numbers for every team, player and umpire are on Baseball Savant.
Why MLB Chose Challenges Instead of Fully Automated Calls
MLB tested fully automated ball and strike calls in the minor leagues, but players and coaches preferred keeping the umpire in charge and using technology only to fix clear misses. The challenge format keeps the human element, keeps pitch framing relevant for catchers and adds strategy, since a team that burns its challenges early can be stuck with a bad call late. It also focuses the technology on the moments that matter most.
The Strike Zone
The automated zone is a two dimensional rectangle measured at the middle of home plate. It is 17 inches wide, the width of the plate, and its top and bottom are set by each batter’s height: the top at 53.5 percent and the bottom at 27 percent. That makes it slightly different from the three dimensional zone umpires have traditionally called, and pitches that clip the front or back of the plate can be judged differently.
Other Recent Rule Changes
ABS is the latest in a run of changes aimed at pace and action. The pitch clock arrived in 2023, along with bigger bases and limits on pickoff attempts and defensive shifts. Those changes cut about 24 minutes off the average game in their first season and brought stolen bases back. Our pitch clock explainer covers those rules.
What It Means for Umpires
Umpires still work every game and call every pitch. What has changed is visibility: every challenged call is shown to the crowd, and umpire accuracy on challenges is now tracked publicly. More on umpire pay is on our MLB umpire salaries page.
Frequently Asked Questions
Does MLB use robot umpires in 2026?
Yes, through the ABS challenge system. Umpires call the pitches, and players can challenge them using automated tracking.
How many challenges does each team get?
Two per game, and a team keeps any challenge that is successful. Teams also get one challenge to start each extra inning.
Can a manager challenge a ball or strike?
No. Only the batter, pitcher or catcher can make a ball or strike challenge.
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MLB’s official announcement of the system is on MLB.com.