Why Olympic Curling Stones Have Two Small, But Very Important, Lights on Them

Cory Thiesse and Korey Dropkin will be trying to win the first-ever gold medal for Team USA in mixed doubles curling on Tuesday. | @NBCSports

Curling becomes a fan-favorite event every four years at the Winter Olympics and that's no different year at the Milan Cortina Games. The stakes are high for Team USA on Tuesday as Cory Thiesse and Korey Dropkin will be facing Sweden in the mixed doubles gold medal match. A win would give America its first-ever gold in this event, which started in the 2018 Games.

If you're new to curling you'll want to catch up on how the scoring works. Also, you might see two little lights on the stones during play and we're here to let you know the important meaning of those lights and what they do.

Curlers have to activate the stone before an attempt by tilting it up off the ice. The two lights will then flash white which means the hog line technology has been activated and it's ready to be played. The hog line is the green line on the ice that the stone must be released before it or a foul will be called and the stone will be removed from play. You don't want that to happen. If the stone is correctly released before the line, the lights will flash green.

Here's a good breakdown of that process:

🚨 You don't want red lights on your curling stone...
🟢 The lights need to stay green for a valid throw!

Let's go over exactly what the lights on the Olympic curling stones are for.#Olympics #WinterOlympics pic.twitter.com/yzMXzmvZvi

— The Olympic Games (@Olympics) February 10, 2026

So there you go. Red light is bad. Green light is good. It's interesting to learn that these stones have so much technology in them but it makes sense because a lot is on the line and this is a great way to make sure nobody gains an extra advantage.

Now you have some fun information to share with your friends while you watch today's huge USA-Sweden match, with starts at 12:05 p.m. ET on USA Network and Peacock.

---