A shared budget is a single average daily budget that several campaigns in one advertising account draw on, instead of each campaign holding its own fixed amount. Google Ads defines it as "a single average daily budget that's shared by multiple campaigns in an account", according to its help centre. The feature exists to solve a dull but costly problem: money sitting idle in a campaign that cannot find enough traffic, while a neighbouring campaign stops showing ads at lunchtime because its own allowance has run out. Pooling the money lets the system move what one campaign leaves on the table to another campaign that is capped. The idea now sits at the centre of a wider argument about how much control advertisers keep over their spend.

How a pooled budget works

The mechanics start in the account's shared library, which holds items usable by several campaigns, such as negative keyword lists. An advertiser creates a shared budget under Tools, then Budgets and bidding, then Shared budgets, gives it a name and an amount, and attaches campaigns, according to Google's instructions. Adding a campaign adds that campaign's existing budget to the pool. Four campaigns with 6 dollars each become one 24 dollar shared budget.

From that point the campaigns stop having individual limits. The pool is an average daily budget, the same unit that governs individual campaigns. That matters because an average daily budget is not a hard daily cap. Since October 4, 2017, Google has allowed spend on a single day to reach twice the daily budget, balanced against a monthly ceiling of 30.4 times the daily figure. A 100 dollar shared budget can therefore spend up to 200 dollars on a busy Tuesday, provided the month as a whole stays within 3,040 dollars.

Inside the pool, Google decides which campaign gets the money. Unused budget is "reallocated automatically" to a budget-capped campaign able to reach enough traffic, according to its help page. Take three campaigns sharing 100 dollars a day: a brand campaign that historically spends 20 dollars, a generic campaign that could spend 60 and a competitor campaign that could spend 50. Run separately with budgets of 20, 40 and 40, the generic campaign would stop early. Pooled, the brand campaign's quiet days release money that the generic and competitor campaigns can absorb. Google publishes no rule guaranteeing any single campaign a minimum share of the pool, which is the source of most complaints about the feature.

A campaign switched to a shared budget midway through the day starts counting from zero at the moment of the switch, Google notes, even if it had already exhausted its own budget.

For developers, the same object appears in the Google Ads API as a CampaignBudget resource with a field called explicitly_shared. When it is set to true, the budget can serve many campaigns and appears in the shared library. The change is one-way: once a budget is explicitly shared, it cannot be turned back into a single-campaign budget, according to Google's API documentation.

Where shared budgets are allowed

Eligibility is narrower than the name suggests. As of October 2026, Google's help page lists Search, Shopping, Display and Video campaigns as eligible, and says other campaign types are not supported "at this time". It names campaigns in an experiment, App campaigns, Hotel campaigns using a commission bid strategy, Performance Max and Smart Shopping as incompatible. Campaigns using a total budget, a fixed amount spent evenly over a set period, cannot join a shared budget either. Google expanded total budgets to Search and Shopping campaigns in January 2026, creating a second budget model that does not mix with pooling.

The incompatibility with Performance Max is structural. A Performance Max campaign already behaves like a pool: as PPC Land's PMax explainer puts it, the format runs on "one budget, one conversion goal" across Search, YouTube, Display, Discover, Gmail and Maps. The pooling happens across channels inside one campaign rather than across campaigns.

Pairing with portfolio bidding

Google's main recommendation is to pair a shared budget with a portfolio bid strategy, which applies one automated bidding goal across several campaigns. The two can now be linked so that the shared budget always covers exactly the campaigns in the portfolio; adding or removing a campaign updates both. Google gives no launch date for the link, which works for strategies with up to 500 campaigns. Google says advertisers using shared budgets with portfolio bid strategies on Search campaigns typically see 13% more conversions, a figure drawn from its own global data between January 2024 and March 2025. The logic is that campaigns sharing both money and a target pool their conversion data, which is why portfolio strategies are presented as a way to group campaigns with shared goals.

Origin and evolution

Google announced shared budgets on the Inside AdWords blog on September 17, 2012. Vidya Iyer of Google's ads engineering team wrote that the option let advertisers "establish a single daily budget that's shared by multiple campaigns", with an example of 100 dollars split across desktop search, mobile search and remarketing. Developers got access in version v201209 of the AdWords API, Google's developer blog noted in November 2012.

Microsoft's search platform, then called Bing Ads, launched its own shared budgets in October 2016, according to its advertising blog. Microsoft's scripting documentation describes the same mechanic: if campaign A has 10 dollars and spends 8, campaign B "would automatically use the 2 dollars that campaign A didn't use". Microsoft later rolled out portfolio bid strategies globally in February 2022, recommending them alongside shared budgets.

Meta took the idea further and more forcefully. Facebook's campaign budget optimisation (CBO), now called Advantage campaign budget, sets one budget at campaign level and distributes it across ad sets. Facebook planned to make it mandatory in 2019, postponed the change twice, and in April 2020 said it had "decided not to pursue a mandatory migration", according to Search Engine Land. PPC Land's campaign explainer traces how Meta's budget level has moved since.

Why the term matters to advertisers

For anyone running dozens of small campaigns, a shared budget replaces daily manual reallocation. It also matters because budgets have become a performance input rather than an accounting line. Since August 17, 2026, Google has steered budget-limited Target CPA and Target ROAS campaigns back towards their stated targets, which Google's Ginny Marvin summarised as the target becoming the efficiency lever in capped campaigns. Whether a campaign is budget-limited now changes how it bids, and a shared budget changes which campaigns are limited and when. Practitioners have since argued publicly that budget is turning into a performance lever, a shift that makes the structure of a pool more consequential than it was in 2012.

Limitations and disputes

The central criticism is loss of control. Because the system decides allocation, one campaign can absorb most of the pool while a lower-volume campaign with a strategic purpose, such as brand defence, receives little. Google provides no per-campaign floor or ceiling inside a shared budget.

Pacing changes can interact with pools in unexpected ways. When Google changed how campaigns with ad schedules pace towards the 30.4 monthly ceiling from March 1, 2026, Sam Hamawi, described as a Google sales representative, called it "a showstopper for shared budgets" in a LinkedIn thread. Google had published no shared-budget guidance for that change.

Reporting is a further weak point. A pool hides which campaign was starved on a given day, and the budget-limited status that triggers bidding changes is harder to interpret when the limit belongs to a group. The 13% conversion uplift Google cites is self-reported and comes from the company that sells the inventory.

Not the same as

  • Portfolio bid strategy: a shared bidding goal across campaigns. It governs how much each auction is worth, not how much money is available; the two are often linked but are separate objects.
  • Campaign total budget: a fixed amount for one campaign over 3 to 90 days, not a pool across campaigns, and not combinable with a shared budget.
  • Advantage campaign budget (Meta) and Microsoft Advertising shared budgets: the closest equivalents. Meta's version pools across ad sets inside one campaign; Microsoft's pools across campaigns, as Google's does. Search Ads 360 offers budget bid strategies that adjust each engine budget daily, which rewrites budgets rather than pooling them.
  • Shared budget as a general phrase: outside paid media it also describes a single marketing budget split between teams or a co-funded budget between a brand and a retailer, which has nothing to do with the Google Ads object.

Recent developments

Today, Google announced channel prioritisation and budget allocation controls, written up by Tal Akabas, director of product management at Google Ads. Advertisers can mark channels as high or low priority and cap low-priority channels at a percentage of daily budget, "on a best-effort basis". The controls are rolling out across Search, Shopping, Performance Max and Demand Gen, and "also apply to shared budgets", Google said. Its help page adds that the allocation applies to a shared budget "as a whole, across all campaigns that use it", and that campaigns in a shared budget must be of identical type for the settings to apply. Google's help page says the rollout starts progressively from October 15, 2026. From February 2027, Search campaigns with the Google Display Network switched on will lose their current spend allocation setup. The change follows a July 2026 alpha in which Google let some Performance Max advertisers switch off search partners and display.

Timeline

  • September 17, 2012: Google announces shared budgets for AdWords on the Inside AdWords blog.
  • November 2012: Shared budgets become available to developers in AdWords API v201209.
  • October 2016: Bing Ads launches shared budgets.
  • October 4, 2017: Google allows daily spend of up to twice the average daily budget, with a 30.4 times monthly ceiling.
  • 2019: Facebook plans to make campaign budget optimisation mandatory, then postpones the change.
  • April 2020: Facebook drops the mandatory campaign budget optimisation migration.
  • February 2022: Microsoft Advertising rolls out portfolio bid strategies globally.
  • January 2024 to March 2025: Period of Google internal data behind its claim of 13% more conversions from shared budgets with portfolio strategies.
  • January 2026: Google expands campaign total budgets to Search, Shopping and Performance Max.
  • March 1, 2026: Google begins changing pacing for campaigns with ad schedules.
  • August 17, 2026: Google begins steering budget-limited Target CPA and Target ROAS campaigns to their targets.
  • October 14, 2026: Google announces channel prioritisation and budget allocation controls that also apply to shared budgets.
  • October 15, 2026: Progressive rollout of the controls begins, according to Google's help page.
  • February 2027: Current spend allocation setup ends for Search campaigns with the Display Network on.

Summary

Who: Advertisers and agencies running several campaigns in one Google Ads account, with equivalents at Microsoft Advertising and Meta. Google operates the allocation.

What: A single average daily budget shared by multiple campaigns, which moves unused money to budget-capped campaigns automatically.

When: Introduced by Google on September 17, 2012; Microsoft followed in October 2016. On October 14, 2026, Google said its new channel prioritisation controls would also apply to shared budgets.

Where: In the shared library of Google Ads, for Search, Shopping, Display and Video campaigns, and in the Google Ads API as an explicitly shared CampaignBudget. Performance Max, App and total-budget campaigns are excluded as of October 2026.

Why: To stop money sitting idle in one campaign while another runs out, reducing manual reallocation, at the cost of control over how the pool is split.