Campaign Budget Optimization (CBO) is a Meta Ads budgeting method where the total budget is set at the campaign level and Meta’s algorithm automatically distributes spend across ad sets in real time based on performance. Rather than manually assigning fixed budgets per ad set, CBO lets the system shift more money toward whichever audience or creative is performing best at any given moment. It is most effective when ad sets are meaningfully different from each other, otherwise the algorithm tends to concentrate all spend on one ad set. CBO is now deeply integrated into Advantage+ campaign structures.