Campaign Budget Optimisation
Meta setting that pools budget across ad sets and allocates dynamically.
Campaign Budget Optimisation (CBO) is Meta's bidding mode in which budget is set at the campaign level rather than the ad-set level, and Meta's delivery system reallocates spend across ad sets dynamically to chase the lowest-cost outcomes.
CBO became the default in Meta Ads in 2019 and has since been augmented by Advantage Campaign Budget. For UK financial advisers it is usually the right default at low-to-medium budgets because it lets Meta's delivery system consolidate learning signals across ad sets rather than fragmenting them.
CBO is the right choice when ad sets share an objective and when the advertiser is agnostic about which audience delivers conversions. It is the wrong choice when the advertiser has strong prior beliefs about which audiences should receive minimum spend (for example, allocating protected budget to a named-introducer retargeting pool), because CBO will starve smaller-signal ad sets and over-fund the cheapest-converting one.
Practical recommendation: use CBO with three to five ad sets per campaign, each with comparable audience size (broad, interest-layer lookalike, value-based lookalike), unified creative pool and aligned objective. Set minimum and maximum spend limits per ad set when protecting strategic segments. Avoid CBO across ad sets with materially different audience sizes or objectives, as delivery becomes unstable.
See also: Advantage+, ad set budget optimisation (ABO), lookalike audiences, value-based bidding.