Behind the scenes of an NHL offside review

When the Vegas Golden Knights scored midway through overtime in Game 4 at the Delta Center Monday night, head coach John Tortorella got all the way to the coaches’ room before someone called him back to the bench.

The play was under a league-initiated review for offside.

While it’s a nightmare for the scoring team, it’s a beacon of hope for the other. And in this case, Utah Mammoth head coach André Tourigny didn’t move an inch when the puck trickled into the net.

He knew there was a chance for the call to be reversed.

The play was, in fact, deemed offside, meaning the teams would play on.

In the end, it didn’t matter, as the Golden Knights would score in the final minute of the first overtime period to win the game and tie the series. The teams now head back to Las Vegas for Game 5.

How does offside work in hockey?

First off — and this is important — in hockey, it’s “offside,” not “offsides.” Calling it the latter is a sure way to out yourself as a non-hockey fan.

With that out of the way, here’s how offside works in hockey.

Simply put, the puck has to fully cross the blue line before any of the attacking team’s players do. You can remember it with the phrase “black over blue before you.”

In the video below, it’s clear that No. 9 in white, Golden Knights forward Jack Eichel, has both feet all the way across the blue line before the puck crosses into the zone. His team scored before the puck exited the zone, so the goal was reversed.

Vegas has its game-winning goal wiped off the board after video review due to offside. pic.twitter.com/uOHayolzHM

— Sportsnet (@Sportsnet) April 28, 2026

There is no penalty associated with offside — just a stoppage in play. The intent is to stop players from cherry-picking. The linesmen are responsible for stopping play as soon as an offside happens, but as humans, they sometimes miss things.

The NHL has been around far longer than video review has even been possible, so for most of the league’s history, if the linesman didn’t catch an offside in the moment, any ensuing goals would count.

But when current Dallas Stars forward Matt Duchene scored a goal after being at least a foot offside in 2013, the pressure intensified for the NHL to institute a review process to cover offside, goaltender interference and a few other things.

It was in place by the beginning of the 2015-16 season, and the league has been a different place ever since. As mentioned, it gives one team a glimmer of hope and the other a pit in its stomach.

There’s one nuance that affected both Monday’s Utah-Vegas game and Sunday’s contest between the Anaheim Ducks and the Edmonton Oilers.

See, throughout the bulk of the game, plays are only reviewed if a team issues a coach’s challenge. It comes with a risk: If you’re wrong, your team takes a two-minute penalty, which could result in your team being down an additional goal.

But in sudden-death overtime, a penalty would not affect the game, as the goal that results from a failed challenge ends the game.

For that reason, every goal scored in overtime or the last minute of regulation — in both the playoffs and the regular season — is automatically reviewed by the league’s situation room for all potential factors. The on-ice officials make the final call based on the angles and information given by the folks in the situation room.