CBO vs ABO on Meta ads.
Which budget setup to use, and how to test it.

What is the difference between CBO and ABO?

The difference is where the budget lives. With CBO, now called Advantage+ campaign budget, you set one budget for the whole campaign and Meta splits it between ad sets as results come in. With ABO, each ad set has its own daily or lifetime budget, and Meta spends that amount on that ad set alone.

Meta says Advantage+ campaign budget may not spend equally across ad sets: with two active ad sets, most of the budget can go to one of them if that gets the best overall result. That is why Meta tells you to read CBO results at the campaign level, not ad set by ad set.

An ad set budget, by contrast, can be spent as soon as delivery opportunities appear for that ad set. You keep control of each amount, and you give up the automatic shifting of money between ad sets.

What is Advantage+ campaign budget?

Advantage+ campaign budget is Meta’s current name for campaign budget optimization. Ads Manager may also show it as Campaign budget, or Budget with Advantage+ on. You set one daily or lifetime budget, and Meta distributes it in real time to the ad sets with the best opportunities, for the whole life of the campaign.

Meta says it is best suited for campaigns with at least 2 ad sets. Sales, Leads and App promotion campaigns have it turned on by default. After you switch it on or off, Meta requires a 2-hour minimum before you can switch it again.

To use it, every ad set in the campaign must share:

• the same budget type, daily or lifetime;
• the same bid strategy: highest volume, bid cap or cost per result goal;
• the same optimization event, if the bid strategy is highest volume;
• standard delivery.

For campaigns without a campaign budget, Meta also offers a middle path: ad set budget sharing, which lets your ad sets share up to 20% of their daily budget with each other while you keep a budget on each one.

When should you use CBO, and when ABO?

Use CBO when your ad sets pursue one goal, you value them equally and you judge success for the campaign as a whole. Use ABO when you must control spend per ad set, when audience sizes differ a lot, or when ad sets mix optimization goals or bid strategies. The table below sums up Meta’s own criteria.

Audience size matters more than it looks. Meta warns that with Advantage+ campaign budget, the ad sets with the largest audiences will likely receive the most budget. Put a small retargeting audience next to a broad prospecting one, and CBO will tend to feed the broad one.

If you choose CBO but still need a floor or a cap on one ad set, Meta lets you set minimum and maximum spend limits per ad set. It also advises using them sparingly: the more budget is locked into specific ad sets, the less room the system has to optimize.

How do you test CBO against ABO?

Test them with a Meta A/B test, not by turning campaigns on and off. Meta’s A/B test shows each version to a separate part of your audience so nobody sees both, then compares cost per result. Build two versions that differ only in the budget setup, and give them the same total budget.

1. Create the A/B test by duplicating your campaign and changing one variable: the budget setup. Keep audiences, ads and the optimization event identical.
2. Give both versions the same budget. Meta recommends it for a fair comparison.
3. Run the test for at least 7 days. Meta says shorter tests may be inconclusive, and a test can last up to 30 days. If your customers usually take more than a week to buy, run it longer.
4. Use an audience you are not targeting in another campaign at the same time. Meta warns that overlap can contaminate results.
5. Judge the CBO version on campaign totals: the number of optimization events and the average cost per optimization event.

Once you pick a side, make your changes in bulk rather than one at a time. Meta notes that each edit can send the campaign back into the learning phase, and that Advantage+ campaign budget can take about 2 hours to adjust after you add an ad set.

Which CBO mistakes does Meta warn about?

The most common one is pausing ad sets by hand. Meta says Advantage+ campaign budget spends on active ad sets only, so pausing one removes it from consideration, and unpausing it later may find no budget left. Meta also advises against pausing ad sets with low delivery, since that can raise your cost per action.

• Stay under 70 ad sets per campaign. Above that, Meta limits the edits you can make after publishing, and 200 is the hard maximum.
• After the first setup, add new ad sets in bulk rather than one by one.
• Use ad set spend limits sparingly, and take care when you combine them with a cost or bid control: too many constraints can stop an ad set from delivering.
• Check that every ad set can actually deliver. An ad set that meets no opportunities gets no budget.

If your ROAS drops after a switch, check the tracking before blaming the budget setup. Our guide on why a Meta ads ROAS drops walks through the checks in order.