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Our founder was watching the Avalanche on opening week when a goal went in and the camera lingered on the puck sitting in the back of the net. It had tiny blinking lights on it. That's not a broadcast glitch, and it's not your eyes. Every puck in an NHL game is a piece of tracking technology, and it's been that way for several seasons now.
What's Inside an NHL Puck
From the outside, a game puck looks like any other: black vulcanized rubber, 3 inches across and 1 inch thick. Inside, it carries a small battery, a circuit board, and infrared emitters that pulse 60 times per second. When the technology launched, the pucks were reported to cost around $40 each, far more than the standard puck you'd buy for practice.
The hardest part wasn't fitting electronics inside. It was making sure the puck still felt and played exactly like a normal puck. Players are famously sensitive to anything that changes how the puck behaves, so the league tested extensively to make sure the new pucks passed.
How the Tracking Works
The NHL's Puck and Player Tracking system became fully operational in the 2021-22 season. Up to 20 cameras mounted around each arena watch for the puck's infrared pulses and detect its position up to 60 times per second. Players are tracked too: emitters in their sweaters are picked up about 15 times per second.
Put together, that produces millions of location data points per game, precise enough to measure how fast a shot was going, how fast a player was skating, how far he traveled during a shift, and how much time the puck spent in each zone.
So Why Could You See It Blinking?
Infrared light is invisible to the human eye, so fans in the arena never see the puck blink. TV cameras are a different story. Many digital camera sensors can pick up near-infrared light that people can't, which is most likely why the lights showed up on your screen when the puck sat still in the net long enough for the camera to catch it.
You can see the same effect at home. Point a TV remote at your phone's camera, press a button, and look at the phone's screen. On many phones, you'll see the remote's invisible infrared light flashing.
Where You See the Data
You've already seen tracking data on broadcasts, like the shot speed that pops up after a hard slap shot, or a skater's top speed on a breakaway. The NHL also opened much of it up to fans through its NHL EDGE website (NHL.com/EDGE), built with data partner Sportradar. There you can look up stats like skating speed, skating distance, shot speed, shot location, and zone time for players, goalies, and teams. It's a fun rabbit hole, especially if you want to see just how fast stars like Connor McDavid really are. (Curious what gear the stars use? See our post on what gear NHL stars use.)
The Puck That Glowed
This isn't the NHL's first smart puck. When Fox Sports had NHL broadcast rights in the 1990s, it introduced FoxTrax, better known as the glowing puck, at the 1996 NHL All-Star Game. FoxTrax pucks were cut open, packed with a battery, a circuit board, and infrared emitters, then bonded back together. Specially synchronized cameras followed the pulses, and Fox drew a blue glow around the puck on screen. On hard shots, a colored comet tail streaked behind it.
Hockey purists hated it. Many fans found the graphics distracting, and some players who tested the puck felt it had more rebound than a normal puck. FoxTrax lasted through the end of the 1997-98 season, and when the broadcast rights moved to ABC in 1998, the glowing puck didn't come along. It's still remembered as one of the strangest experiments in sports TV, but the idea behind it, tracking the puck electronically, turned out to be ahead of its time.
The Long Road to Today's Puck
Between the glowing puck and today's system, the NHL spent years testing tracking technology. Before the league-wide launch, it tested a system with Germany's Fraunhofer Institute, which even included a special freezer to store, charge, and test the pucks between uses. Some players, including Jack Eichel, voiced concern that chip-filled pucks might behave differently than the ones they'd grown up with. The league kept refining the technology until it became a standard part of every game in 2021-22.
Light-Up Pucks for the Rest of Us
You won't find an NHL tracking puck at the store, but there are fun light-up pucks for kids and night games on the driveway. They use visible LEDs, so you can actually see them glow, which is closer to Fox's glowing puck than to the NHL's invisible tracking lights. Shop light-up pucks → For serious off-ice practice, the Green Biscuit is still our favorite: it glides on pavement like a real puck on ice. See it on Amazon → And for regular game and practice pucks, see the Accessories section of our Pro Shop.
Next time a puck sits in the net long enough for the camera to zoom in, look closely. That blinking light means the puck has been measuring the game the whole time.