The standard model (SM) predicts that the $W$ boson decays equally to all three flavours of leptons, known as lepton flavour universality. Many studies have been performed to measure the rate at which the $W$ boson decays to different flavors of leptons to test this accidental symmetry. Because of the high mass of the $\tau$ lepton, the measurement of the ratio between the branching fraction of $W$ bosons in $\tau$ and $\mu$ channels is a good probe for physics beyond the SM. We report the results on lepton flavour universality from different experiments