The luminosity measurement is among the leading sources of experimental uncertainties in SM precision physics at LHC, for example for measurement of fiducial cross-sections of W, Z and Higgs. The LHC experiments target 1% uncertainty on the yearly calibrated offline luminosity. In this talk we report the measurement of the integrated luminosity in proton-proton collisions at a center-of-mass energy of 13.6 TeV in Run 3 with the CMS experiment. Various subdetectors (luminometers) provide a stable and linear measurement of object rates at a wide range of instantaneous luminosity. Each luminometer is calibrated from beam-separation scans with the van der Meer method. The total preliminary uncertainty achieved (including calibration, stability and linearity sources) on the integrated luminosity is 1.4% for 2022 and 1.3% for 2023.