From traditional to digital media, the growth of false information, hoaxes or rumors has recently crystalized in the formulas " fake news " or " alternative facts " , which indicate a certain weakening of critical thinking. These formulas reveal that the public sphere experiences complex epistemo-logical processes, an even more complex relationship to truth and a profound modification of ale-thurgies. This paper will analyze the " life " of false information in a changing media environment, first by defining what the terms " fake news " and " alternative facts " mean, before subsequently analyzing a recent case study involving different levels of false information and forgeries during the French election, the macronleaks. We will observe the ambiguous role of social networks and the strategies deployed by some actors to decipher false information. Therefore, our aim is to offer a semio-political analysis of " fake news " and " alternative facts " that will help us understand why we are so eager to believe in them, and what to do about them.