If a playoff is needed to determine the winner of the 150th Open Championship in St. Andrews, the first, second, 17th and 18th holes will be used.

The Open is employing a four-hole aggregate playoff on the Old Course, if there is a tie at the top following regulation. If players are still deadlocked after those four extra holes, they will repeatedly play the 18th hole in sudden death.

Officials used a three-hole system in 2019 and '21 (the championship was canceled in 2020 because of the pandemic), but said the aggregate number depends on the venue. At St. Andrews, that number is four as it works perfectly for the course's routing.

The most recent Open playoff came in 2015, the last time the Old Course played host. Zach Johnson birdied the first and second holes, and followed that with a bogey-par finish to defeat Louis Oosthuizen and Marc Leishman.

Beginning with 1989, when Mark Calcavecchia defeated Greg Norman and Wayne Grady at Royal Troon, The Open has used an aggregate extra session. Prior to that, the championship used both 18- and 36-hole playoffs during different eras. The Open has been decided 21 times in a playoff. The first time, technically, was in 1876.

By comparison, the Masters uses sudden death; the PGA Championship, a three-hole aggregate; and the U.S. Open, a two-hole aggregate.