Remove unused vertices from a subdivision surface

You can use Clean Topology to remove any vertices that were created but not used in a subdivision surface. Removing the extra, unused vertices helps to reduce the file size and improve interactive performance.

For example, if have refined some regions of a subdivision surface, but moved only a few of the vertices created by the refinement, Clean Topology can remove the vertices you did not transform.

To automatically reduce unused vertices in a subdivision surface

Select the surface whose unused vertices you wish to remove.
Select Subdiv Surfaces > Clean Topology.
Any unused vertices are removed from the subdivision mesh.

Notes

Clean Topology only removes a vertice if it meets all three of the following requirements:

No edits to the position of the vertice. That is, if a face has been moved the associated vertices will not be removed.
No mapping or edits to the UV associated with a vertice. That is, if any texture data is applied to the vertice it will not be removed.
No crease applied to the vertices or edges

There may be some vertices that Clean Topology cannot remove, even if they meet these requirements, because the vertices are required for surface topology.

If you use Subdiv Surfaces > Clean Topology after creating a Blend Shape or other deformation, you might get areas on the surface that have no UVs. These areas are the result of vertices created when you weight the deformer while the Clean Topology node still exists in construction history.
Avoid using Clean Topology after creating deformers. Also delete history after using Clean Topology so that it does not interfere with the creation of deformers.