
A significant part of dark matter could be compact, in particular in the form of primordial black holes. I will review the signatures of primordial black holes, both in the form of gravitational-wave events and as gravitational lenses of fast radio bursts. Alternatively, a diffuse dark-matter component could interact with baryons. I will explain how these interactions cause heating of the baryons, becoming observable prior to the epoch of reionization.