Higgs couplings and quantum numbers

The Higgs boson couplings and quantum numbers remain central targets of the ATLAS and CMS physics programs at the CERN LHC. Since the 2012 discovery, both experiments have steadily improved measurements of Higgs production and decay, allowing increasingly sensitive tests of its spin, parity, and interaction structure. We will present Run 2 results and early Run 3 measurements that illuminate the Higgs boson's quantum numbers using both inclusive rates and differential kinematic information. We highlight the usage of off-shell production, matrix-element methods, and effective field theory interpretations, which have opened new handles on possible deviations from Standard Model expectations. We also summarize the Di-Higgs program, whose sensitivity to the Higgs self-coupling offers an essential complementary probe of the potential modification to the scalar sector. Looking ahead, the unprecedented precision and dataset of the High-Luminosity LHC will significantly enhance sensitivity to subtle deviations in Higgs couplings, quantum numbers, and self-interactions, deepening our understanding of electroweak symmetry breaking and its possible extensions.