When do March Madness brackets lock? Deadline and more ahead of NCAA tournament

March Madness is officially underway, as the First Four kicked things off on Tuesday and the first round set to begin on Thursday.

While the deadline to submit March Madness brackets varies based on the site or app that's being used, the latest any site accepts brackets is before the first game of the first round.

The field of 64 teams has been finalized after the Wagner Seahawks pulled off a 71-68 victory over the Howard Bison on Tuesday. That was followed by the Colorado State Rams blowing out the Virginia Cavaliers 67-42.

The Grambling State Tigers got things started on Wednesday, needing overtime to pull off an 88-81 victory over the Montana State Bobcats, while the Colorado Buffaloes followed with a 60-53 win against the Boise State Broncos.

While college basketball fans will look to fill out a perfect bracket, time is running out to do so. Take a look at when March Madness brackets lock below.

---

More about March Madness brackets locking

The NCAA website lists their deadline as noon ET on Thursday. Meanwhile, other sites have a 12:15 p.m. ET deadline as first round action will begin at that time when the Mississippi State Bulldogs take on the Michigan State Spartans.

There are plenty of sites that offer rewards for a perfect bracket, or even for the closest to a perfect bracket. There has never been a verified perfect March Madness bracket, with the odds of predicting each game are just one in 9,223,372,036,854,775,808.

Gregg Nigl, a neuropsychologist from Columbus, Ohio, holds the record for the longest perfect bracket, as he predicted the first 49 games correctly in 2019. His streak lasted until the Sweet Sixteen when the Purdue Boilermakers beat the Tennessee Volunteers 99-94 in overtime.

Before Nigl's bracket, the longest streak was 39 games, which took place in 2017. The Boilermakers also ended that streak, knocking off the Iowa State Cyclones 80-76 in the second round. In the three NCAA Tournament's since Nigl's impressive run, there hasn't been a single bracket to survive the opening round.

For those looking for a lucrative prize, there are sites giving away up to $1 million for a perfect bracket. The highest such prize ever offered came in 2014 as Berkshire Hathaway CEO offered $1 billion to anyone who could perfectly predict each game of the NCAA Tournament.