The image everyone associates with VAR offside calls — thin red and blue lines drawn across a frozen replay — is actually the tail end of a much more technical process, and the version arriving at the 2026 World Cup replaces a meaningful chunk of that human line-drawing with automated 3D positioning. The gap between “VAR checked it” and “the system called it” is bigger than most broadcasts make it look.
What’s actually tracking the players
Advanced Semi-Automated Offside Technology relies on 16 dedicated optical tracking cameras mounted around the stadium, running continuously alongside the standard broadcast feeds. Those cameras don’t just capture footage — they feed a system that builds a real-time 3D positional model of every player on the pitch, effectively an AI-generated avatar of each athlete’s exact skeletal position, refreshed dozens of times per second. Combined with the tracking data, a sensor embedded inside the match ball detects the precise instant of a kick, which is the critical timestamp the entire offside calculation depends on — because offside is a purely positional question at one exact moment, not an average or a trend.
The actual calculation: geometry, not judgment
Once the ball-touch instant is identified, the system pulls every player’s exact 3D position at that specific frame and computes the offside line automatically — a genuinely different process than a human VAR operator manually placing lines on a 2D broadcast image, which is what earlier offside-review systems actually did. The technology stack behind this is specific and non-trivial: camera calibration across all 16 units, pose estimation for each player, multi-view geometry to reconcile all the camera angles into one 3D model, continuous tracking, and sensor synchronization between the ball and the camera network — all of which has to agree before the system will generate a call.
Why 10 centimeters is the real threshold
The system doesn’t flag every marginal position — it’s specifically calibrated to alert match officials only when a player is offside by more than 10 centimeters, a deliberate threshold built to separate genuinely clear infractions from positions close enough that they warrant human review rather than an automated call. For those clear cases, the system sends an automated audio alert directly to on-field officials, a meaningful change from the 2022 World Cup version, where the same positional data went to the video assistant referee first rather than the pitch officials directly — cutting a step (and time) out of the review chain.
The actual takeaway
VAR offside calls are no longer primarily a human drawing lines on a paused replay — they’re the output of a real-time 3D tracking system reconciling 16 cameras, a ball sensor, and continuous player pose estimation into one geometric calculation, run automatically the instant the ball is touched. The 10-centimeter threshold is the actual dividing line between “the system decides” and “a human still has to look,” and it’s the specific number worth knowing next time a call gets contested — because for anything closer than that, the technology was designed to defer to a person, not override one.
