This is a US, multi-center, randomized, double-blind, double-dummy, Phase 3b study to evaluate efficacy of remibrutinib (25 mg twice daily \[b.i.d.\] by mouth \[p.o.\]) compared to dupilumab (600 mg loading dose administered subcutaneously (s.c.) followed by 300 mg every 2 weeks s.c.) at early timepoints (4 weeks and earlier), when administered as an add-on treatment to second generation H1-antihistamines (sgH1-AH) (standard label dose as background therapy) in adult US participants with moderate to severe chronic spontaneous urticaria (CSU) inadequately controlled by sgH1-AHs.