Examples include compressed extent versions. Examples may create an empty target virtual volume tree having a tree structure of a source virtual volume tree of a source storage system, the source virtual volume tree comprising source base and source snapshot virtual volumes, each representing respective versions of a plurality of extents, wherein each of the extents corresponds to a different portion of an address space of the source base virtual volume. Examples may include compressed extent collections, each comprising a compressed representation of multiple populated versions of a single extent from the source base and snapshot virtual volumes, the multiple populated versions compressed relative to one another.