A pitch can look like a strike on TV and still be called a ball because the rulebook zone, an umpire’s judgment, the broadcast graphic, and MLB’s ABS challenge test are not identical. In MLB’s 2026 challenge system, the home-plate umpire makes the initial call; the batter, pitcher, or catcher can then immediately ask for a review of that call.
What makes a pitch a strike?
The strike zone is not simply the rectangle drawn on a television screen. The 2019 edition of MLB’s Official Baseball Rules describes a three-dimensional zone over home plate, defined in relation to the batter’s stance. That PDF is a historical 2019 edition, so it should not be treated as confirmation of every detail in the rules currently in force.
In practice, the umpire behind home plate judges each pitch and calls it a ball or strike. The call can be difficult to assess from a single camera angle: the ball travels through space, while a TV graphic is only a visual reference. MLB says the human-called zone tends to be more rounded than the rectangular zone used for ABS challenges.
How MLB’s ABS challenge zone works in 2026
MLB’s 2026 ABS system reviews eligible challenges rather than automatically replacing the umpire’s call on every pitch. The challenge zone is a two-dimensional rectangle evaluated where the pitch passes the middle of home plate. MLB’s stated dimensions for the zone are:
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- Width: 17 inches.
- Top: 53.5% of the batter’s measured height.
- Bottom: 27% of the batter’s measured height.
MLB says any part of the ball touching that rectangle counts as a strike for the challenge. Because the height limits are calculated from the individual batter’s height, the vertical boundaries are not one fixed height for every player. The dimensions were described in MLB’s 2025 announcement of the system for the 2026 season.
These are the ABS challenge boundaries, not a restatement of the rulebook’s three-dimensional definition. The distinction matters when a call looks close: the rulebook description, umpire judgment, and challenge test are related, but they are not interchangeable measurements.
Why a TV strike-zone box may not settle the call
A broadcast box can help you follow a pitch, but it is not proof of the official ABS result. MLB says the challenge zone is evaluated at the midpoint of home plate, whereas televised graphics have historically shown a zone at the front of the plate. A two-dimensional overlay also cannot, by itself, show the pitch’s full path through the three-dimensional space of the rulebook zone.
So if the ball appears to clip a TV box—or miss it—treat that as an aid to viewing, not a definitive measurement. The challenge result is based on MLB’s tracking system and the defined challenge zone, not a fan’s ability to reproduce the measurement from an ordinary broadcast angle.
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Who can challenge, and what happens?
MLB announced the challenge format for Major League Spring Training, Championship Season, and Postseason games beginning in 2026. The umpire makes the initial call. Only the batter, pitcher, or catcher may request a challenge, and it must happen immediately after the call; dugout staff cannot initiate one.
- A call is made. The home-plate umpire initially rules the pitch a ball or strike.
- An eligible player requests review. The batter, pitcher, or catcher signals immediately after the call.
- ABS checks the pitch. MLB says 12 Hawk-Eye cameras track pitch location. The result is shown to the crowd and broadcast.
- The call is confirmed or overturned. A successful challenge changes the call, and the team keeps that challenge. An unsuccessful challenge is lost.
Each club starts a game with two challenges. Under MLB’s announcement, a team entering an extra inning with no challenges remaining receives one for that inning. MLB described the challenge process as taking approximately 15 seconds; that is an approximate duration, not a guarantee for every review.
How the human call and ABS challenge differ
| Aspect | Umpire’s initial call | ABS challenge |
|---|---|---|
| What defines the zone | The rulebook describes a three-dimensional zone over home plate; the umpire judges the pitch. | A two-dimensional rectangle defined for the challenge system. |
| Where the pitch is assessed | The umpire judges the pitch in play; the historical 2019 rules PDF describes the zone over the plate. | At the middle of home plate, according to MLB’s 2026 system description. |
| Vertical boundaries | The historical rulebook definition relates the zone to the batter’s stance. | MLB specifies the top and bottom as percentages of the individual batter’s measured height. |
| Who decides first | The home-plate umpire. | The system supplies a review result only after an eligible player challenges. |
| Effect of review | The initial ruling stands unless challenged successfully. | A successful challenge overturns the call and is retained; an unsuccessful challenge is lost. |
The 2019 rulebook PDF supports the historical rulebook description in the table; MLB’s 2026 guide and system announcement describe the challenge operation and dimensions.
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What the reported challenge figures do—and do not—show
MLB.com’s 2026 guide reports results from MLB’s 288-game 2025 Spring Training experiment. In that experiment, 52.2% of challenged calls were overturned. Reported success rates were 56% for catcher challenges, 50% for hitter challenges, and 41% for pitcher challenges. MLB.com also reported an average of 4.1 challenges per game and an average of 13.8 seconds per challenge.
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Those figures describe the 2025 Spring Training experiment, not the 2026 regular season. They should not be read as predictions for any particular call or as settled 2026 season-wide performance.
The same MLB.com guide cites a 2-2 count example in which MLB research put the umpire-called zone at 449 square inches and the ABS zone at 443 square inches. That is an example for a particular count and context, not a universal measurement showing that one zone is always larger.
What the technology does
MLB says the system uses 12 Hawk-Eye cameras to track pitch location, with Hawk-Eye technology also used in Statcast. Its 2025 announcement also identifies a private 5G network from T-Mobile for Business’ Advanced Network Solutions. The camera tracking and network support the review process; the outcome is still determined against the defined challenge zone.
MLB said the result is displayed to fans in the stadium and on the broadcast. Its September 2025 announcement quoted Commissioner Robert D. Manfred Jr. saying that players’ strong preference for a challenge format over technology calling every pitch was a key factor in the decision. That is MLB’s stated rationale for adopting the format.
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For the system description and boundaries, see MLB’s September 23, 2025 announcement, the 2026 ABS overview, and the Baseball Savant ABS dashboard.
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