Comparison between the UGC and QSOC redshifts. Grey dots correspond to all redshifts in common between the two tables, while black dots are restricted to those with flags_qsoc = 0, which corresponds to a higher reliability subset. The red curve denotes identical predictions in the two modules. Yellow curves highlight mismatches between common quasar or AGN emission lines, as explained in Delchambre et al. (2023), while the blue vertical lines show constant predictions by QSOC.