ABO= Budget is set at the ad set level
CBO= Budget is set at the campaign level.
ABO allows for more precise spending. You can force spend to specific ad sets/ ads. There are several reasons you might do this: if you want to force spend to be split between 2 geographic locations, 2 pieces of creative for a strict A/B test or other reasons.
CBO gives Meta’s algorithm the freedom to spend the budget where it pleases. The system shifts spend between ad sets and ads until it finds the top performers, then it will concentrate spend on those.
CBO is recommended by most advertisers as it makes the most of your budget and reduces the chance you will spend a lot of money on an ad that doesn’t work.
Do you use ABO or CBO in your campaigns?