How do the qualifications to the World Cup work in

 each continent?

          The World Cup qualifiers is the process realized before each World Cup to choose the teams that are going to make part of the tournament.

It's been organized by FIFA  since 1930  and the qualification system has changed through the time because of the increase of the teams that have joined FIFA during the years.

At the moment 209 teams are trying to qualify for the 2018 Russia World Cup, while in the first World Cup (1930 in Uruguay) only 13 teams participated because they were the only members of FIFA. 

• Qualification system of UEFA (Europe):

           The qualification system of the UEFA is divided in two rounds.

In the first round the teams are divided randomly in 9 different groups of 6 teams. Each team has to play two matches against each team of their group, one at home and the other one away.

Points system:

• 
• If a team wins a match it wins 3 points
• If it draws it wins 1 point
• If the team loses it gets no points

After playing all the matches, the team with most points is directly qualified for the World Cup, while the eight 2nd best teams of each group have to play a second round.

The 8 teams are divided in 4 elimination group's in which they have to play a away and a home game. the winners of each group get's qualified. 

• Qualification system of CONCACAF （North & Central America and Caribbean）：

           The CONCACAF qualification system has three different rounds。

The first round is a small tournament of three rounds have teams play home-and-away over two legs. A first preliminary round involved the 14 lowest ranked teams and the seven winners advanced to the second round. The 13 higher ranked sides received byes in the second round and were joined by the seven first round winners; the ten winners advanced to the third round. Two higher ranked teams received byes in the third round and were joined by ten second round winners; the six winners advanced to the preliminary group stage.

The remaining 12 teams play in 3 semifinal groups of 4 teams with the top two in each group advancing to a final six-team group.

The final round – often referred to as the "hexagonal" because there are six teams involved – will see the top three teams advance to the World Cup finals, while the fourth placed side will enter an inter-confederation play-off for a final World Cup spot.

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• Qualification system of CONMEBOL （South America）:

           The CONMEBOL qualification system is the simplest of all. It only consist of a single group in which all the teams of the confederation are part of .

All the teams have to play a home and a away game against all the other participants. The points system is the same that is used by UEFA. 

The four best teams are directly qualified， while the fifth placed team will enter an inter-confederation play-off for a World Cup spot.

• Qualification system of CAF （Africa）：

           The CAF qualification system starts with two preliminary rounds （to narrow the distance of 53 teams to 20）

After the preliminary rounds are finished the teams are divided in 5 different groups of 4，and only the  group winners are qualified。 

                                                                                                                                                                                                   

• Qualification system of AFC：

           The qualification system of the AFC have to do 4 different rounds： 

            

• First round: A total of 12 teams (teams ranked 35–46) will play home-and-away over two legs The six winners will advance to the second round。

• Second round: A total of 40 teams (teams ranked 1–34 and six first round winners) will be divided into eight groups of five teams to play home-and-away matches. The eight group winners and the four best group runners-up will advance to the third round.

• Third round: The 12 teams which advance from the second round will be divided into two groups of six teams to play home-and-away matches. The top two teams of each group will qualify, and the two third-placed teams will advance to the fourth round.

• Fourth round: The two third-placed teams of each group from the third round will play home-and-away over two legs. The winner will advance to the inter-confederation play-offs.

• Qualification system of OFC（Oceania）：

            The qualification system of OFC has 4 rounds：

• First round: the four lowest countries in the FIFA ranking will play a tournament at a single country. The winner will advance to the second round.

• Second round (OFC Nations Cup): A total of eight teams, and the first round winner) will play the tournament at a single country. For the group stage, they will be divided into two groups of four teams. The top three teams of each group will advance to the third round of World Cup qualifying. The top two teams of each group will also advance to the knockout stage (semi-finals and final) to decide the OFC winner。

• Third round: The six teams which advance from the second round will be divided into two groups of three teams to play home-and-away round-robin matches. The two group winners will meet in a two-legged match with the winner advancing to the inter-confederation play-offs。