In context
You run a campaign with $300/day CBO budget and 4 ad sets. Meta shifts spend in real-time — ad set 2 (winning angle) might take $180, ad set 4 (weak angle) gets $30. You don't have to manually rebalance. Downside: you can't force a specific ad set to spend a specific amount.
Why it matters
- CBO optimizes toward lowest-CPA ad set automatically.
- CBO requires trusting Meta — no manual intervention mid-flight.
- Works best with 3-6 ad sets; too many ad sets starves some.
Related terms
Frequently asked questions
CBO vs ABO — when to use which?
CBO for scaling known-good angles, ABO for cold testing where you want forced budget floor per angle.
Does CBO work with 1 ad set?
Yes, but it's equivalent to ABO. CBO's power only emerges with 2+ ad sets.
Can I set min/max per ad set in CBO?
Yes — use ad set spend limits, but use sparingly; it defeats the purpose.