Each tie was played over
two legs, with each team playing one leg at home. The team that scored more goals on aggregate over the two legs advanced to the next round. In the event that aggregate score finished level, the
away goals rule would be applied, i.e., the team that scored more goals away from home over the two legs advanced. If away goals were also equal, then thirty minutes of
extra time would be played, divided into two fifteen-minutes halves. The away goals rule would again be applied after extra time, i.e., if there were goals scored during extra time and the aggregate score was still level, the visiting team would advance by virtue of more away goals scored. If no goals were scored during extra time, the tie would be decided by
penalty shootout. In the draws for each round, teams were seeded based on their 2012
UEFA club coefficients, with the teams divided into seeded and unseeded pots. A seeded team was drawn against an unseeded team, with the order of legs in each tie decided randomly. Due to the limited time between matches, the draws for the second and third qualifying rounds took place before the results of the previous round were known. The seeding in these draws (or in any cases where the results of a tie in the previous round were not known at the time of draw) was carried out under the assumption that the higher-ranked teams of the previous round would advance to this round, which means if a lower-ranked team were to advance, it would simply take the seeding of its defeated opponent. Prior to the draws, UEFA may form "groups" in accordance with the principles set by the Club Competitions Committee, but they were purely for convenience of the draw and for ensuring that teams from the same association were not drawn against each other, and did not resemble any real groupings in the sense of the competition. ==Teams==