X-ray line searches are sensitive probes for many dark matter models, such as sterile
neutrino dark matter in the nuMSM. I will review current status of the experimental
efforts, including that of the tentative signal at 3.5 keV. Then I will discuss some
recent progress with NuSTAR and its prospects in the near future. Finally I will talk
about the idea of dark matter velocity spectroscopy, a powerful diagnostic tool for
tentative dark matter line signals, which is achievable with high-resolution
spectrometers.