Faithful transitive permutation representations of groups are a widely used tool to study groups, as these capture the structure of the group and can be represented as a graph. Faithful transitive permutation representations can be seen as the action of the group on one of its core-free subgroups, being the degree of the permutation representation equal to the index of the core-free subgroup on its parent group. The GAP package CoreFreeSub allows you to compute the set of core-free subgroups, their indexes and represent the faithful transitive permutation representations as graph exported in DOT. In this talk, we will present these functionalities and how these can be used.