Principal media buying expands amid budget pressure

Forrester said principal media buying is expanding in advertising, as agencies buy inventory at undisclosed discounts and resell it to advertisers.

The research described the practice as an increasingly central feature of media buying. It linked the trend to budget pressure on marketing teams and a push for greater cost control in paid media.

Forrester said 52% of marketing decision-makers anticipate further budget constraints. It also cited an average chief marketing officer tenure of 3.9 years.

Growing usage

Forrester said 47% of marketers already use principal media. It said 81% of US B2C marketing executives plan to increase their use in 2026.

The firm described principal media as a model that changes how risk and margin move through the ad supply chain. Agencies take inventory positions and then sell placements onward, rather than acting only as an agent arranging buys for a disclosed fee.

Forrester said advertisers can secure media placements at rates up to 10% below market standards under this approach. It said agencies can absorb inventory risk as part of the arrangement.

Advertiser trade-offs

The research said principal media can offer lower costs and improved predictability for advertisers. It also framed the practice as a way for marketers to shift financial risk to agency partners.

Forrester said agencies use proprietary data and access to exclusive inventory as part of these deals. It stated that this can change how performance optimisation works within media buying. It also said the model places new weight on outcome guarantees rather than unit prices, such as cost per thousand impressions.

Advertisers have criticised principal media in the past due to concerns about transparency and potential conflicts of interest. In principal trading models, the agency can act as both seller and adviser, which raises questions about whether a client receives the best available deal in the wider market.

Forrester said marketers should treat the model as a commercial arrangement that requires clearer guardrails than traditional buying. It recommended updated contracts that specify operational transparency. It also recommended spending caps of 10% to 20% of the total media budget for principal media activity.

Agency economics

Forrester said principal media provides agencies with an additional source of margin. It said this has become more important as marketers scrutinise fees and as agencies face pressure on service pricing.

It also said publishers and other media owners can use principal deals for more predictable sales. It stated that the approach can offer guaranteed demand and access to deals that might not otherwise be available through standard buying routes.

The report said the practice has become a structural feature of the market rather than a short-term anomaly. It also noted that agencies and publishers view it as a stabilising revenue mechanism during a period of fragmentation across channels and measurement approaches.

Calls for transparency

Forrester said transparency determines whether principal media works effectively for advertisers. It recommended consistent performance metrics across all media buying activity, including principal deals.

It also recommended separating planning and buying teams. It said this reduces conflicts of interest when an agency both advises on channel selection and sells inventory that it owns or controls.

Forrester said agencies should provide clear business cases for each principal buy. It also said teams should focus on performance outcomes rather than "cheap CPMs".

Forrester positioned the trend within a wider shift in marketing procurement. It said marketing leaders want predictable spend and reduced exposure to under-delivery. It said principal models offer one route to those outcomes when structured with explicit terms and reporting.

Jay Pattisall set out the firm's view of the direction of travel for the market.

"Principal media isn't a loophole - it's the inevitable outcome of an industry addicted to efficiency and under relentless budget pressure," said Jay Pattisall, VP, Principal Analyst, Forrester.

"Despite the controversy, principal media has become a business mainstay because it delivers what CMOs need most: predictable costs, guaranteed outcomes, and budget relief," Pattisall, co-author of the report, added.

Pattisall also mentioned that in an AI-pressured fee environment, agencies are leveraging principal media as a financial lifeline to subsidise inexpensive services.

"The real shift isn't toward cheaper CPMs, it's toward outcome‐guaranteed buying that mitigates advertiser risk," said Pattisall.