How Advantage campaign budget works
Normally you give each ad set its own money. With Advantage campaign budget you hold a single budget at the campaign level instead, and Meta’s delivery system decides how much of it each ad set gets, hour by hour, based on where it predicts the cheapest results are available right now.
The name changed but the mechanism did not. This is what the industry called campaign budget optimisation, and you will still hear people say CBO in meetings, in old blog posts and in agency reports. If someone talks about turning CBO on, they mean this setting.
The split is not fixed and it is not fair. An ad set that looks promising early can take most of the budget while others barely spend. You can set minimum and maximum spend limits per ad set to force a wider spread, but every limit you add narrows the freedom the system needs to do its job, so use them as guardrails rather than as a plan.
Why it matters
It changes what a comparison means. When each ad set holds its own budget, two audiences spending the same amount can be compared directly. Under a campaign budget they never spend the same amount, so an audience with a poor cost per result may simply have been given the difficult hours or the leftover impressions.
It also matters for accounts with small budgets, which is most advertisers working in Nepal and most small businesses anywhere. Splitting a modest budget across many ad sets leaves each one too thin to learn from. Holding the money in one place and letting the system concentrate it is usually the more sensible choice, because concentration is what small accounts lack.
Common mistakes
Putting unlike things in one campaign is the big one. If a cold audience sits beside a warm retargeting audience under a shared budget, the warm one will look cheaper because the people in it already know you, and the system will feed it. You end up paying to reach existing visitors while new-customer reach quietly stops.
The second mistake is judging an ad set that never got spend. Nothing meaningful can be read from a handful of impressions. The third is nudging the budget up and down every day; each change unsettles delivery and buys another unstable stretch instead of a result.
How to act on it
Group ad sets that deserve to compete. Same stage of the funnel, same offer, same country. If two audiences should not be judged against each other, they belong in different campaigns, not in different ad sets under one budget.
Judge results at the campaign level. The question is what a customer cost you overall, not which ad set won an internal race the system was rigging on purpose. Use minimum spend limits only when you have a real reason to keep an audience alive, such as testing a market you intend to enter, and change the budget in steps with days between them. Where budgets are large enough that this allocation drives real money, it is worth reviewing the structure as part of ongoing Meta ads management rather than tinkering weekly.