Shared budget

Instead of $30 on each of three campaigns, you set $90 once, and Google spreads it during the day toward the campaigns with more search volume or opportunity. It is handy when you care about the total, not the split. The trade-off is control: a broad, high-volume campaign can take most of the money while a smaller, more profitable one gets little.

Where you'll see it

In Google Ads, shared budgets are under Tools > Shared library > Budgets, where you create one and assign campaigns to it. In the Campaigns table, a campaign on a shared budget shows the shared budget's name in the Budget column. Meta's equivalent is Advantage+ campaign budget, shared across one campaign's ad sets; TikTok offers Campaign Budget Optimization across ad groups.

Worked exampleThree campaigns on $90 a day, one month

Campaign	Spend	Conversions	CPA
A, brand	$300	30	$10
B, generic	$2,100	35	$60
C, competitors	$336	6	$56

Campaign B took $2,100 of the $2,736 total, about 77%. If the brand campaign was held back by the shared budget, giving it its own budget could protect the cheapest conversions.