W mass and width measurements at LEP2

The LEP2 program, operating at centre-of-mass energies above the W+W−W+W− production threshold, has allowed for precision measurements of the W boson mass and width. Results are presented here for a total luminosity of about 2300pb−1−1, corresponding to the 91% of the data taken at LEP2. The most important sources of systematic uncertainty are described, focussing on some recent progress in their understanding and evaluation. A new analysis from the OPAL collaboration dedicated to extract the mass from the purely leptonic channel is also presented.