  The measurements of the inclusive and differential fiducial cross sections of
the Higgs boson decaying to a pair of photons are presented. The analysis is
performed using proton-proton collisions data recorded with the CMS detector at
the LHC at a centre-of-mass energy of 13 TeV and corresponding to an integrated
luminosity of 137 fb$^{-1}$. The inclusive fiducial cross section is measured
to be $\sigma_\mathrm{fid}$ = 73.4 $_{-5.3}^{+5.4}$ (stat) ${}_{-2.2}^{+2.4}$
(syst) fb, in agreement with the standard model expectation of 75.4 $\pm$ 4.1
fb. The measurements are also performed in fiducial regions targeting different
production modes and as function of several observables describing the diphoton
system, the number of additional jets present in the event, and other kinematic
observables. Two double differential measurements are performed. No significant
deviations from the standard model expectations are observed.
