  We discuss the possibility of successful magnetogenesis during inflation by
employing the one-loop effective action of massless QED. The action is strictly
non-local and results from the long distance fluctuations of massless charged
particles present at the inflationary scale. Most importantly, it encodes the
conformal anomaly of QED which is crucial to avoid the vacuum preservation in
classical electromagnetism. In particular, we find a blue spectrum for the
magnetic field with spectral index $n_B \simeq 2 - \alpha_{\text{e}}$ where
$\alpha_{\text{e}}$ depends on both the number of e-folds during inflation as
well as the coefficient of the one-loop beta function. In particular, the sign
of the beta function has important bearing on the final result. A low reheating
temperature is required for the present day magnetic field to be consistent
with the lower bound inferred on the field in the intergalactic medium.
