Major League Baseball’s Automated Ball/Strike challenge system made its regular-season debut on March 25, 2026. Under the system, home plate umpires still call every pitch, but certain ball and strike calls can be challenged and reviewed by the computer.
How the system works
According to MLB and AP, stadiums use cameras to track each pitch and determine whether it passed through the strike zone over home plate. In the challenge format, each team gets two challenges per game and keeps a challenge if the review is successful.
Only the pitcher, catcher, or batter can start a challenge, and it has to happen immediately after the pitch. The signal is a tap of the hat or helmet. The dugout and other players on the field cannot call for a review.
What changes in extra innings
Teams that have no challenges left entering an extra inning are guaranteed one challenge in that inning. Source material also says teams that lose both of their initial challenges will receive one additional challenge in each extra inning.
Where MLB tested it
AP reported that automated ball-strike technology has been tested in the minor leagues since 2019, with recent use at Triple-A since 2022, during MLB spring training, and at the 2025 All-Star Game in Atlanta.
AP also cited spring training results showing that more than half of challenges were successful.