
Free-riding starts at formation
It is easy to treat social loafing as a problem with individual students. More often it is baked in at formation: teams that are too big, too lopsided, or thrown together with no shared availability make it easy for someone to disappear and hard for the rest to notice.
Get the team right and a lot of free-riding never starts, because there is nowhere to hide and no one is set up to carry everyone else.
Right-size the team
Bigger teams make free-riding easier. Keep teams to a size where the work cannot be done by a subset, so everyone's contribution is visible and load-bearing. Three to five is the usual sweet spot for university projects.