Adult staphylinoids are generally small beetles no more than a few millimetres long, though Staphylinidae can reach 50 mm long and Silphidae can reach 45 mm.

[2] Adults can be recognised by the hind wings having no accessory posterior ridge (locking device), no medial loop, no wedge cell and no apical hinge.

[1] Larval staphylinoids have 3-segmented (rarely 4-segmented) maxillary palps with distinct (often fused) galia and lacinia.

[1] Staphylinoidea contains the following subgroups:[3][4][5][6] The unambiguous fossil record dates back to Triassic, and an early Mesozoic origin of the group is probable.

[7] A 2019 molecular phylogenetic study confirmed the monophyly of Ptilidae and found that it is sister group to Hydraenidae.