Comparison of the fiducial photometric redshift to the photometric redshift obtained from three combinations of Euclid and ancillary photometry. In each panel, the catastrophic outlier fractions (OLFs) are reported for two fiducial redshift bins, z = 1–6 and z = 6–8. The OLF represents the fraction of sources with |z_sim − z_fid|/(1 + z_fid) > 0.15. The outlier identification boundaries are indicated with solid red lines. The data points are presented as 2D histograms with bin size Δz = 0.1. The colour bar corresponds to the number of galaxies in each bin and is the same for all panels. The solid orange line is the identity curve. Data outside the two solid red lines are identified as catastrophic outliers.