  We present an incremental version (4FGL-DR2, for Data Release 2) of the
fourth Fermi-LAT catalog of gamma-ray sources. Based on the first ten years of
science data in the energy range from 50 MeV to 1 TeV, it uses the same
analysis methods as the 4FGL catalog did for eight years of data. The spectral
parameters, spectral energy distributions and associations are updated for all
sources. Light curves are rebuilt for all sources with 1-year intervals (not
2-month intervals). Among the 5064 4FGL sources, 120 are formally below the
detection threshold over 10 years (but are kept in the list), while 53 are
newly associated and four associations were withdrawn. We report 723 new
sources, mostly just above the detection threshold, among which two are
considered identified and 341 have a plausible counterpart at other
wavelengths.
