MLB's ABS System Explained: How 12 Cameras, 5G, And A Tape Measure Are Changing Baseball
During Spring Training 2025, Major League Baseball has required all players to undergo an independently verified, standardized height-measurement protocol.
The rules are super strict: players can’t wear hats or shoes. Backs must be firm against the wall with knees exposed. Independent testers first conduct manual measurements, which are then verified against biomechanical analysis. And to account for potential loss of height throughout the day due to spinal compression from gravity and physical activity, MLB is even requiring all of its teams to take measurements between 10 am and 12 pm local time on their appointed day.
As a result, we’ve already started to see significant shrinkage. For example, Gavin Lux apparently got three inches shorter over the winter, going from 6’2” in 2025 to 5’11” in 2026. Bo Naylor also lost three inches, while Alex Bregman and Bryce Harper lost two. And while the overwhelming majority of players are seeing a downward revision in their listed height, Shohei Ohtani actually got taller, with his official measurement increasing his listed height from 6’3” to 6’4” this year.
But MLB isn’t doing this to embarrass its players or to ensure that its gameday programs are accurate. MLB is doing this because its new Automated Ball-Strike (ABS) Challenge System relies on accurate measurements down to the millimeter.
For 150 years, MLB has determined whether a pitch was a ball or a strike through a subjective, umpire-dependent, and officially irrefutable method. But beginning this week on Opening Night 2026, which will be streamed live on Netflix for the first time in history, balls and strikes will now be contestable, machine-verifiable, and displayed in real time on a 4K jumbotron — all within just 10 to 15 seconds.
So for today’s newsletter, I’m going to make you an expert on MLB’s ABS system. We’ll start by talking about how the 12-camera setup actually works and why the MLB umpires’ union ultimately agreed to implement it. But then I want to get into the good stuff, including what seven years of testing data tells us about the system’s accuracy, how much time these challenges will add to each game, and what pitchers and hitters can do to exploit the system’s technological limitations.
Let’s get into it…