Notes. The order in which the catalogs are listed reflects the order in which we merged the catalogs. As the 4FGL-DR4 catalog is used as the first added catalog, there is no catalog against which it would be checked for duplicates; therefore, no match radius is listed. The radius given for the other catalogs is then used to filter for duplicates against all the previously added catalogs (therefore, e.g., only 1724 sources from the BZCAT are added, since the other sources are already part of the 4FGL-DR4 catalog within 4″). The horizontal line divides the catalogs of confirmed blazars from those containing only blazar candidates. N_sources: Total number of sources contained in each catalog. N_{sources, inital}: number of initially new sources added to BLAZE catalog, taking into account duplicates from the previous catalogs within the match radius listed in column “Match radius”. N_{sources, original}: number of sources from each catalog after applying quality cuts. (1) Abdollahi et al. (4FGL-DR4; 2022); (2) Massaro et al. (2015); (3) Chang et al. (2019); (4) Sbarrato et al. (2026); (5) Marcotulli et al. (2025); (6) Flesch (2023); (7) D’Abrusco et al. (2019); (8) Paggi et al. (2020); (9) Itoh et al. (2020).