Top panel: XMM-Atlas vs. eFEDS fluxes in the 0.5–2 keV band. The solid blue line shows the one-to-one relation. The dotted blue lines correspond to a flux ratio of 6. Sources with fluxes that differ by more than this factor in the two surveys are shown in blue. Bottom panel: distribution of the flux difference of X-ray sources between the XMM-ATLAS and eFEDS observations. The blue line shows a Gaussian distribution with zero mean and unity scatter. The histogram of the normalised flux difference has more power in the wings than in the normal distribution, which we attribute to variability.