You can find the Official Regulations here: https://www.gothiacup.se/regulation/
Classes G13 and B13 play 9-a-side (one goalkeeper and 8 players). The same rules as in 11-a-side are applicable, note that the offside rule is applicable just as in 11-a-side football. The size of the goals is the same as in 11-a-side football. The size of the field is regulated by the Swedish Football Federation’s rules for ”Large 9-a-side”, i.e 72x55 meter.
Number of players and substitution
Teams may use a maximum of 16 players in a 9-a-side match, 9 players on the field and 7 substitutes. A substituted player may reenter in the match.
In 9-a-side ball size 4 will be used.
In 9-a-side, one (1) dispensation is by default given for one overaged player, who can be at most one year over the age limit. Note that it’s not allowed to have more than one overaged player in the roster, who change places in the squad for each game.
Girls may play in boys classes as long as the regulations for age categories are followed.