The Champions League is one of the world’s biggest club competitions, and it has featured some of the most memorable matches in soccer history. From a low point following the Heysel Stadium disaster in 1985 to becoming the most watched tournament in the world in 2021, there’s been plenty of drama in the final 16 in recent years.
Unlike most major international tournaments, Champions League does not have a single-elimination format. Teams meet in home-and-away games, known as legs, with the team that scores more goals over the two meetings advancing to the next round.
After some experimentation with multiple group stages, the competition returned to its original format in 2003-04. Thirty-two clubs qualify for the group stage, and a randomized draw assigns them to eight groups of four teams. A restriction on placing two or more teams from the same national league in the same group and a coefficient-based seeding system ensures competitive balance. Teams earn three points for a win, one point for a tie, and zero points for a loss.
The top team in each group advances to the knockout phase, where they are ranked again according to their UEFA coefficient. A re-draw determines the bracket for the quarterfinal and semifinal rounds, which are played over two legs. If the aggregate score in a tie is level, extra time and the away-goals rule are applied to determine the winner.
Until the 2024-25 season, the best finishers in the league phase were guaranteed to play the second leg of their round-of-16 match at home. From this season on, a draw is made to determine the order of play in the knockout phases after the league phase, diluting the value of finishing higher in the standings.