As the name suggests, international qualifiers are tournaments to determine which nations qualify for the World Cup. The number of spots available for each continent is decided by FIFA, and then each continental federation begins its own qualifying tournament, usually using a group stage to decide which teams will progress into the finals.
The top team from each group qualifies automatically, while the runners-up will compete in a second round of four-team groups. The winners of that phase will book one of the two remaining spots, while the second-placed teams will go into an intercontinental play-off with four Nations League teams.
Each qualifying tournament generally involves a series of matches – either over home and away legs, or in a single-legged tie – to decide the eventual winner. If a match finishes level on aggregate after 90 minutes, extra time and a penalty shootout may be used to determine the winner. In the case of a single-legged tie, teams may host one leg and play an away match at a neutral ground in the other.
The process of qualification is complicated by the fact that some countries are not eligible to compete in a particular tournament. This is because they do not meet the minimum continental federation membership requirements, which are set by FIFA. Exceptions can be made by the respective continental governing body, and these countries are often included in regional competitions to ensure that they have as many opportunities as possible to qualify for major events.