Vector boson scattering is the rarest particle physics process that has been observed at the LHC. After the discovery of a light Higgs boson, it was clear that there will not be spectacular signs of new physics in VBS, however, due to the intricate cancellation in the amplitudes it remains a highly sensitive probe for new physics effects. We will describe the parameterization of new physics effects in terms of Effective Field Theory higher-dimensional operators, and discuss the issues from validity and perturbative unitarity that make EFT a tool difficult to handle for VBS. As an alternative method, we present simplified models for new physics comprising all possible (regarding their spin- and isospin quantum numbers) resonances that could couple to the diboson system. We will discuss both longitudinal as well as transversal couplings to new physics.
