What is the MLB ABS Challenge System?

The debate over “robot umps” is about to take a big step forward. Major League Baseball announced that the ABS Challenge System will be used in all ballparks beginning with the 2026 season, ending years of speculation about if—and how—technology would become part of calling balls and strikes.

The move comes after extensive testing in the Minor Leagues, Spring Training, and at this year’s All-Star Game. The Joint Competition Committee gave its approval in late September, with Commissioner Rob Manfred noting that the feedback loop of fans, players, and managers was key to the decision. Players, in particular, favored the challenge format over a fully automated strike zone.

How the ABS Challenge System Works

The system isn’t a full handover to “robot umps.” Home-plate umpires will still make the calls, but pitchers, catchers, or hitters can request a review if they think one was missed.

• Each team starts with two challenges per game.
• If the game goes to extras, a team out of challenges earns one new challenge each inning.
• The challenge must be immediate—no waiting for a manager’s signal.
• A quick tap of the helmet or cap notifies the umpire.
• Hawk-Eye tracking and T-Mobile’s private 5G network confirm the pitch location within seconds.
• The call is shown on the stadium video board and broadcast for fans to see.
• Teams keep their challenge if correct, but lose it if the umpire’s call stands.

On average, these reviews took about 14 seconds in Spring Training games, with players challenging roughly 2–3 pitches per game.

Key Things Fans Should Know

• Postseason too: ABS will be in use throughout October.
• Who can challenge: Only pitchers, catchers, and batters. Managers can’t.
• Strike zone definition: 17 inches wide, with the top at 53.5% of the player’s height and the bottom at 27%.
• Comparison to human zone: The automated zone is a bit tighter, especially up top, meaning some pitches that umpires have traditionally called strikes may no longer get the call.

What It Means for Baseball

The ABS Challenge System represents a compromise: technology is there to get the big calls right, but umpires still control the flow of the game. It adds a layer of strategy too—teams have to be smart about when to use a challenge and when to hold onto it for a bigger moment.

Starting in 2026, fans will get a new wrinkle in the drama of every pitch. The strike zone won’t be entirely robotic, but it will be more accountable than ever.