The group stage comprises 32 clubs, 22 of whom are direct entrants while ten qualify via the play-offs.
Ten play-off winners join the 22 automatic entrants in the group stage draw at the Grimaldi Forum, Monaco, where the 32 sides are split into four seeding pots and one from each is drawn into the eight groups. Seeds are based on UEFA's coefficient system and no team can meet another from the same association.
Where two sides from the same association qualify, they are paired to split their matches between Tuesday and Wednesday, so one club will always play at home on one day and the other will play away on the other day. In the case of associations with three representatives, only two teams are paired in terms of their fixtures; in the case of associations with four representatives, two pairings are made based on the TV audience.
To ensure sides from the same country play on separate days, the eight groups are distinguished by colour: Groups A–D red and Groups E–H blue. When a paired club is drawn, for example, into one of the red groups, the other paired club – once it is drawn – is automatically assigned to one of the four blue groups.
Teams from Pot 1 are provisionally placed in the first position within their groups, sides from Pot 2 provisionally take the second spot in their sections, and so on. Once the draw is completed, a computer draw determines the final position of the clubs within their group and therefore the order of the home and away matches