Upon further review, the ABS Challenge System has been confirmed for the 2026 MLB season.
The Joint Competition Committee voted Tuesday afternoon to bring the Automated Ball-Strike (ABS) Challenge System, powered by T-Mobile, to the big leagues following several years of experimentation in the Minor Leagues and use in MLB Spring Training and the All-Star Game this year.
“The previous rule changes that have been adopted by the Joint Competition Committee have had staying power and created momentum for the game,” MLB Commissioner Rob Manfred said in a statement. “We used the same process with ABS that started with listening to fans, conducting extensive testing at the Minor League level, and trying at every step to make the game better. Throughout this process we have worked on deploying the system in a way that’s acceptable to players. 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.”
Considered a middle ground between so-called “robot umps” that could call every ball and strike and the long-standing tradition of the natural human error that comes with human umps, the ABS Challenge System gives teams the opportunity to request a quick review of some of the most important ball-strike calls in a given game.
The ABS Challenge System runs on a 5G private network from T-Mobile for Business’ Advanced Network Solutions.
Though MLB has had various iterations of video replay review going back to 2008, this will be the first instance within the championship season at the game’s highest level in which the home-plate umpire’s ball-strike calls will not be ironclad.
With Hawk-Eye technology running in the background and monitoring the exact location of each pitch, relative to the batter’s zone, players can request a challenge of a ball or strike call they feel the umpire got wrong.
When a call is challenged, the Hawk-Eye view is then transmitted over a 5G private network from T-Mobile’s Advanced Network Solutions and nearly instantaneously shown to those in attendance via the videoboard and to home viewers via the broadcast. The ball-strike call is then either confirmed or overturned, and the game goes on having only been briefly interrupted.
“We’ve accomplished a lot through our longstanding partnership with MLB, and the rollout of ABS — powered by T-Mobile 5G — is one of our most exciting milestones yet,” said Mike Katz, president of marketing, strategy and products at T-Mobile. “It’s a powerful example of how we’re using our technology to help MLB innovate, while preserving the character of the game we love. And it’s only possible with the scale and reliability of America’s Best Network.”
Here’s a review of how the ABS Challenge System works and the particulars of the system that will be used in MLB.
How many challenges does each team receive?
Each team will start the game with two challenges apiece.
Do teams get an extra challenge in extra innings?
If a game goes into extra innings, any team that starts the extra inning out of challenges will get one challenge for the 10th inning. If they exhaust that challenge, they will then get another challenge for the 11th, and so on. If a team has challenges remaining at the start of the 10th inning, they will not get an additional challenge for that inning, though they will for any subsequent inning if they are out of challenges at the start of the inning.
Will the ABS Challenge System be in use for every MLB game at every ballpark?
Yes.
And during the postseason?
Also, yes.
Who can issue a challenge?
The batter, the pitcher or the catcher can challenge an umpire’s call. No one else — no, not even the manager — may do so.
Challenges must be made immediately after the umpire’s call, without assistance from the dugout or other players.
How is a challenge issued?
The player taps his cap or helmet to alert the umpire to his desire to challenge the call.
How is the call reviewed?
An animated pitch result graphic is shown to those in attendance via the video board and to home viewers via the broadcast.
How much time does the review add to the game?
In 288 games with the ABS Challenge System during Spring Training 2025, there were an average of 4.1 challenges per game, and those challenges took an average of 13.8 seconds.
Are successful challenges retained?
Yes. A team only loses its challenge if the umpire’s call is confirmed.
Because challenges can be lost, it is incumbent upon the player to be judicious about asking for a challenge (i.e., not “wasting” it in a low-leverage spot so that it is available to his team in a high-leverage spot). So in that sense, the ABS Challenge System adds strategy to the sport.
How was the Challenge System received in Spring Training?
Of the fans surveyed by MLB in Spring Training, 72% said the Challenge System had a positive impact on their experience. Moving forward, 69% of those surveyed said they would like the sport to go ahead with ABS, vs. 31% in favor of continuing with human umpires.
How long was this tested in the Minor Leagues?
The full ABS system was first used in the independent Atlantic League in 2019. The Challenge System was first used in the Florida State League in 2022. During the 2023 and 2024 Triple-A seasons, both the Challenge System and full ABS were tested. By the end of 2024, full ABS had been pushed aside in favor of the Challenge System, which continued to be used in 2025.
Why the Challenge System and not full ABS?
Minor League (MiLB) testing revealed a clear preference among fans, players, managers and other personnel for the Challenge System. The reason, in so many words, is that fans and baseball people still desire a human element of umpiring that involves feel for the game. In MiLB games featuring full ABS, walks were more prevalent, causing games to drag on (and countering the improvements in pace made by the pitch clock).
Also, the art of pitch framing — a craft catchers have studied and in many cases mastered — would go away with full ABS. This is a change the players generally do not support.
The Challenge System is seen as a way to get more of the most important calls correct without dramatically altering the sport overnight. It is a middle ground between full ABS and tradition.
How did MLB arrive at allowing two challenges per team?
At the MiLB level prior to 2025, MLB experimented with three challenges per team per game and two challenges per team per game. Three-challenge games had an average of 5.8 challenges per game, while two-challenge games had an average of 3.9 challenges per game.
In surveys of fans at Triple-A games, 71% said the optimal number of total challenges per game is four or fewer. Two-challenge games met this criteria 62% of the time, while three-challenge games met it only 30% of the time.
How often are challenges successful?
During Spring Training, players challenged 2.6% of all called pitches, and the overturn rate was 52.2%. This was higher than the 50% overturn rate at Triple-A this year.
Interestingly, during Spring Training, defensive players (pitchers and catchers) were more successful in their challenges (54.4%) than hitters (50.0%).
Also, as was the case in MiLB, the overturn rate generally tended to decline as the game went on – from 60% in innings one through three to 51% in innings four through six to 43% in innings seven and eight to 46% in inning nine.
How is the ABS strike zone measured?
Like the plate, it is 17 inches wide. The top end of the zone is at 53.5% of the player’s height, while the bottom is at 27% of the player’s height. The depth of the zone is 8.5 inches from both the front and back of the plate.
How does this compare to the human umpire zone?
The umpire-called zone has generally been more rounded and more lenient to pitchers, with a 55.6% max up top and 24.2% minimum at the bottom.
As an example of the impact this can have on a key call, MLB research found that, in 2-2 counts, the umpire-called zone was 449 square inches, while the ABS zone was 443 square inches.
How does the ABS zone account for different player heights?
All position players in Spring Training camps have their heights measured – first by a team of independent testers conducting manual measurements, then by representatives from a research institute using biomechanical analysis to confirm the manual measurements and safeguard against potential manipulation.
Players are measured standing straight up without cleats.
