2p x-ray absorption spectroscopy of 3d transition metal systems

•This review provides an overview of the different methods and computer codes that are used to interpret 2p x-ray absorption spectra of 3d transition metal ions.•The basic parameters are introduced and an overview is given of the methods used., including both semi-empirical multiplet codes and first-principle codes.•One section is devoted to the user friendly interfaces that have been written on the basis of these codes.•We discuss the first principle codes based on band structure, cluster calculations and wavefunction based methods.•The link between theory and experiment in discussed, including the open issues in the spectral analysis.