Apart from Republic of Ireland, all remaining 54 UEFA member national teams entered the qualifying competition.[2] Players born on or after 1 January 2002 were eligible to participate. Starting from this season, up to five substitutions are permitted per team in each match.[3] Moreover, each match has a regular duration of 90 minutes, instead of 80 minutes in previous seasons.
The qualifying competition consists of two rounds:[4]
Qualifying round: Apart from England and Germany, which receive byes to the elite round as the teams with the highest seeding coefficient, the remaining 52 teams are drawn into 13 groups of four teams. Each group is played in single round-robin format at one of the teams selected as hosts after the draw. The 13 group winners, the 13 runners-up, and the four third-placed teams with the best record against the first and second-placed teams in their group advance to the elite round.
Elite round: The 32 teams are drawn into eight groups of four teams. Each group is played in single round-robin format at one of the teams selected as hosts after the draw. The eight group winners and the seven runners-up with the best record against the first and third-placed teams in their group qualify for the final tournament.
The schedule of each group is as follows, with two rest days between each matchday (Regulations Article 20.04):[4]
In the qualifying round and elite round, teams are ranked according to points (3 points for a win, 1 point for a draw, 0 points for a loss), and if tied on points, the following tiebreaking criteria are applied, in the order given, to determine the rankings (Regulations Articles 14.01 and 14.02):[4]
Goals scored in head-to-head matches among tied teams;
If more than two teams are tied, and after applying all head-to-head criteria above, a subset of teams are still tied, all head-to-head criteria above are reapplied exclusively to this subset of teams;
Goal difference in all group matches;
Goals scored in all group matches;
Penalty shoot-out if only two teams have the same number of points, and they met in the last round of the group and are tied after applying all criteria above (not used if more than two teams have the same number of points, or if their rankings are not relevant for qualification for the next stage);
Disciplinary points (red card = 3 points, yellow card = 1 point, expulsion for two yellow cards in one match = 3 points);
UEFA coefficient for the qualifying round draw;
Drawing of lots.
To determine the four best third-placed teams from the qualifying round and the seven best runners-up from the elite round, the results against the teams in fourth place are discarded. The following criteria are applied (Regulations Articles 15.01, 15.02 and 15.03):[4]
The draw for the qualifying round was held on 6 December 2017, 09:00 CET (UTC+1), at the UEFA headquarters in Nyon, Switzerland.[5][6]
The teams were seeded according to their coefficient ranking, calculated based on the following (a four-year window was used instead of the previous three-year window):[7]
Each group contained one team from Pot A, one team from Pot B, one team from Pot C, and one team from Pot D. For political reasons, Russia and Ukraine, Spain and Gibraltar, Serbia and Kosovo, and Bosnia and Herzegovina and Kosovo would not be drawn in the same group.[2]
The Northern Ireland v Slovakia match, kick-off on 24 October, 13:00 TRT, was abandoned after 13 minutes due to adverse weather conditions, with the remainder of the game played on 25 October, 13:00 TRT. The Turkey v San Marino match, scheduled for kick-off on 24 October, 16:30 TRT, was also postponed due to adverse weather conditions, and rescheduled to 25 October, 15:00 TRT.[8]