The standard model 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 $\tau$ lepton, the measurement of the ratio between $\tau$ and $\mu$ channels is a good probe for physics beyond the standard model. We report the results existing across different experiments, and some ongoing studies on the topic