This chapter describes how spectroscopic measurements differ when moving to x-ray free electron lasers (XFELs) and presents some examples of how these novel x-ray sources have been applied to date. It focuses on the primary differences between storage ring sources and XFELs for time-resolved measurements. Storage ring time-resolved measurements fall into two categories: low (kHz) and high (MHz) repetition rate experiments. The approach of scanning the incident monochromatic x-ray energy is feasible at all the currently available and planned XFEL facilities. One of the techniques applied at XFELs to record as much information as possible in a single measurement is single-shot transmission x-ray absorption spectroscopy (XAS). The high energy resolution off-resonant spectroscopy (HEROS) relies on a combination of wavelength dispersive spectroscopy and x-ray scattering from core electrons for incident x-ray energies below the electron binding energy.