The identification of impurities and the investigations into their behaviour in magnetically confined plasmas as well as the plasma parameter determination belong to the most important applications of x‐ray spectroscopy in the JET and ASDEX tokamaks. Broad‐band flat crystal monochromators—supported by impurity monitors and calibration devices—enable impurity concentration and plasma radiation loss measurements over a wide range of atomic numbers, while high‐resolution spectroscopy offers plasma ion temperature and rotation measurements.