The technique relates to a method for preparing a nanomesh metal membrane 5 transferable on a very wide variety of supports of different types and shapes comprising at least one step of de-alloying 1 a thin layer 6 of a metal alloy deposited on a substrate 7, said method being characterized in that said thin layer 6 has a thickness less than 100 nm, and in that said de-alloying step 1 is carried out by exposing said thin layer 6 to an acid vapor in the gas phase 8, in order to form said nanomesh metal membrane 5.