Regions (red areas) in the footprint of the OGLE-IV RR Lyrae stars (violet symbols) that we used to estimate the completeness, contamination, and percentage of new discoveries of the final clean catalogue of DR3 RR Lyrae stars (orange symbols) in the LMC, SMC, and in the Galactic bulge. For the LMC, we used a circular region with 8.3° in radius centred at (RA=81.5° Dec=−70.1°), for the SMC a region with 5.6° in radius centred at (RA=13.2°, Dec=−72.9°), and for the MW bulge, we used two regions with 3° degree in radius centred at (RA=274.7°, Dec=−31.8°; bulge-up) and (RA=261.2°, Dec=−24.9°; bulge-down).