  Gravitational waves (GWs) are signals that propagate across large distances
in the Universe, and thus, they bring information on the cosmic history. GW
sources are at the same time distance indicators and tracers of the matter
field. Events generated by binary systems can be divided into bright standard
sirens, when followed by electromagnetic transients from which the redshift of
the source can be measured, and the more numerous dark standard sirens, when
counterparts are not available. In this proceeding, I will discuss some methods
for testing the cosmological model using either bright or dark sirens and their
combinations with other cosmological probes, focusing on some of my own recent
contributions.
