Precision calculation of Neff in the Standard Model

The effective number of neutrinos, Neff, is a key parameter in the standard Lambda-CDM cosmology, parametrising the amount of radiation in the early universe and therefore acting as a crucial probe of light and feebly interacting hidden sectors. In this seminar, I will briefly review standard effects that impact the theoretical prediction for Neff in the Standard Model. I will then discuss recent works studying whether higher-order QED corrections can significantly impact this prediction.