abstract: (Affine) W-algebras are a family of vertex algebras defined by Drinfeld-Sokolov reductions. We introduce free field realizations of W-algebras by using Wakimoto representations of affine Lie algebras, which we call Wakimoto representations of W-algebras. Then W-algebras may be described as the intersections of kernels of screening operators. As applications, parabolic inductions for W-algebras are obtained. This is motivated by results of Premet and Losev on finite W-algebras. In type A, this becomes a chiralization of coproducts by Brundan-Kleshchev. In type  BCD, we also have analogs of the coproducts in special cases.