||This article is a stub. You can help the osu!wiki by.|
A guest difficulty is a contribution from one mapper to another mapper's mapset.
Etiquette in the community can make it difficult for multiple mappers to upload maps of the same song around the same time, so a different mapper interested in mapping that song may choose to contribute a difficulty to the other mapper's set instead. They might also decide 'after the fact' upon playing the other map that they like the music and want to create a difficulty for it. Or alternatively, they don't want to put in the effort involved in creating many difficulties, so they just create one and give it to another mapper.
Sometimes, a mapset's owner might request guest difficulties for their mapset, either to make it feel like more of a community effort or because they don't want to create that many difficulties themselves.