The tournament is played on a
knockout format, with 31 teams participating. Initially 23 teams were allocated direct vacancies to enter the competition, with another 8 teams joining the competition via
Champions League qualification. On 21 June 2021, a drawing of lots in
Luxembourg City,
Luxembourg, determined the team's pairing for each match. Each team plays a home and an away match with result points awarded for each leg (3 points for 3–0 or 3–1 wins, 2 points for 3–2 win, 1 point for 2–3 loss). After two legs, the team with the most result points advances to the next round. In case the teams are tied after two legs, a is played immediately at the completion of the second leg. The Golden Set winner is the team that first obtains 15 points, provided that the points difference between the two teams is at least 2 points (thus, the Golden Set is similar to a tiebreak set in a normal match). ==Participating teams==