WTF is sell-side decisioning? | How SSPs are making programmatic more valuable and efficient

Meanwhile, supply-side platforms (SSPs) have operated as infrastructure at the execution level, primarily responsible for packaging and passing along impressions according to instruction. Despite their access to troves of rich audience data insights, these platforms have been largely left out of the strategic decision-making. Rather, they have functioned as a bridge, connecting publishers with marketers and optimizing publishers’ revenue in the process.

However, a new generation of AI-powered, performance-driven decisioning is emerging on the sell side — one that brings intelligence, optimization and audience insights closer to the origin of the impression. Instead of waiting for a bid to determine the value of an eyeball, SSPs can now evaluate signals like page context, content quality and first-party data and apply that information to make decisions upstream without introducing latency.

“For many years, SSPs were focused on integrating with publishers across different channels and formats. Now, we’re seeing a number of different companies exploding onto the scene, with different innovations,” said Mike McNeeley, svp of product at Index Exchange. “A lot of companies are realizing that it can be easier to integrate and implement on the sell side, because they’re basically connecting to all of the supply. There are newer, upgraded integration options, and you can work with every DSP as well.”

In this WTF explainer guide, Digiday and Index Exchange explore what sell-side decisioning is, how it’s reshaping the programmatic supply chain and how both media buyers and owners can benefit from smarter, faster and more efficient supply.

Sell-side decisioning refers to the practice of applying intelligence — informed by data, algorithms and creative technology, plus business logic at the SSP level — to a bid request before it reaches the DSP. 

Supply-side platforms have less than 10 milliseconds to evaluate an ad opportunity and create a bid request. Historically, it was unimaginable to leverage that window to make the types of nuanced decisions that typically occur on the buy side.

Thanks to advancements in cloud infrastructure, parallel processing and edge computing, there’s now plenty of room in the pre-bid window for SSPs to tap signals from across the open internet and apply intelligence before the bid is placed, without disrupting the rest of the transaction flow.

Traditionally, within the programmatic marketplace, the buy side and the DSP ad tech that places bids have held most of the power. DSPs have determined if an impression aligns with a marketer’s brand and whether it can reach the intended audience and produce the desired results. The sell side, on the other hand, hasn’t played much of a role in that process and might not even know why it received a bid in the first place.

Unlike those traditional models, sell-side decisioning turns the SSP into a dynamic decision engine. It uses machine learning, data signals and campaign objectives to pre-curate and optimize supply, thereby reducing waste and improving the quality of each impression opportunity. Because the publisher or supplier has a more intimate knowledge of the nuances of its own inventory, the SSP surfaces only the most relevant impressions for a given campaign, making every bid request more valuable.

This means fewer assumptions about factors such as page-level information, the context of content and audience. For example, one type of data logic that can now be applied on the sell side is targeting, or excluding, specific page URLs rather than broader domain names, according to Index Exchange’s McNeeley. 

“Through some of the new tools, they can do page-level targeting and page-level exclusions, and that’s been really powerful,” McNeeley said. “Publishers will send their global placement IDs, which are the individual ad units that are available for sale, and folks can basically say, ‘Okay, I’m going to calculate viewability scores for this individual ad unit on mobile devices, on desktop computers or on laptop computers.’ They can add in, potentially, scores for Android phones versus iOS phones. Wherever the content and the experience is changing for the consumer, those scores are going to change — viewability, click-through rate, attention, you name it. So, there’s a lot of innovation happening there.”

Audience-level targeting can be done at a more granular level through sell-side decisioning as well, McNeeley said. Publishers can create specific audiences based on the data available through eIDs (extended identifiers). There are approximately 15 eID providers globally that advertisers use.

“If you have a customer that wants to work with a DSP, but they don’t support one eID provider that you want to test in streaming TV, for example — if it’s supported on the sell side, you can enable it through the same DSP you want to work with,” McNeeley said. “Ultimately, it’s using data from both the buy side and the sell side and combining it into one solution for brands and publishers.”

Here’s a step-by-step guide to how sell-side decisioning differs from traditional programmatic ad buying. 

Steps to traditional programmatic marketplace transactions:

• Marketer defines the campaign objective and sets targeting criteria within a DSP
• DSP connects to ad exchanges and SSPs where publishers offer ad inventory
• SSPs decide which ad inventory to send to a DSP 
• DSP bids on ad impressions that meet the marketer’s set criteria
• DSP with the highest bid wins, and the ad is displayed to the consumer within the publisher’s content

Steps to sell-side decisioning transactions applying additional intelligence via SSP: 

• Marketer defines the campaign objective and sets targeting criteria within a DSP
• DSP connects to ad exchanges and SSPs where publishers offer ad inventory
• Sell-side decisioning — used in partnership between the sell side and the buy side — applies additional machine learning, data signals, custom AI algorithms to enrich relevant impressions or help inform bidding decisions for a campaign, making every bid request more valuable
• DSP bids on ad impressions that meet the marketer’s set criteria
• DSP with the highest bid wins, and the ad is displayed to the consumer within the publisher’s content

Ultimately, sell-side decisioning allows publishers to better assess and optimize the value of their inventory before a bid is even made. Supply-side platforms that support sell-side decisioning are thus able to shift from being passive pipes to acting as performance engines that help publishers drive more revenue, unlock yield from high-performing impressions and reduce waste from poorly matched bids or unsold inventory.

While AI platforms can provide custom algorithms to optimize ad campaigns, publishers can now pass their own signals to buyers. They can enable sell-side decisioning to allow marketers to use publishers’ first-party data to target audiences in a privacy-safe way. “A custom AI algorithm company, for example, can decide when to turn on and when to turn off certain deals for their buyers,” McNeeley explained. “But the publishers could also pass them signals to use in that decisioning to help them make better choices.”

Publishers can also pass individual pricing to marketers, which can be more value-expressive than open real-time bidding. And publishers can make industry-specific data available through sell-side decisioning. 

The Weather Company makes its ad inventory available to the programmatic marketplace by integrating with an SSP, but it also makes its weather-specific data available through sell-side decisioning. “By activating data through curated deals, they’re unlocking new revenue streams and giving marketers a smarter, more scalable way to connect with audiences — all while prioritizing performance, privacy and precision,” McNeeley said.

Demand-side platforms are tasked with evaluating millions of bid requests per second from dozens of SSPs, each representing a possible impression. But many of the impressions are duplicative or misaligned with campaign goals. Because the full funnel of supply is available to select from through sell-side decisioning, SSPs, DSPs and brands can work together more effectively to achieve shared goals. 

“The biggest DSPs are trying to do a lot to meet marketers’ needs,” McNeeley said. “They’re working across channels. They’re in different formats. They’re competing with walled gardens and others to do optimization and measurement. Their roadmaps are stressed.”

To protect system stability and maintain cost efficiency, DSPs impose strict limits on how many queries per second (QPS) they’ll accept from each supply source. While necessary, this throttling introduces a major tradeoff: The DSP might never see some of the best-performing impressions simply because they were filtered out before a bid could be placed. 

Sell-side decisioning helps alleviate this pressure by allowing SSPs to apply intelligence earlier in the process, scoring and curating impressions before they hit the DSP. This ensures that what does get through the queries-per-second filter is more relevant, higher quality and more likely to drive results — allowing for more comprehensive data discovery by searching for data at the top of the funnel, prior to optimization. 

The result for DSPs is twofold: reduced infrastructure strain and improved campaign performance. With less noise and more signal, DSPs can spend more time optimizing bids and less time filtering impressions that never should have reached them in the first place.

This gives buyers the ability to purchase impressions that better align with their campaign goals without having to invest in custom-developing their own DSP. For example, a buyer’s marketing strategy could be focused on streaming ads. Sell-side decisioning’s curation capabilities might give a buyer access to a new vendor innovating in streaming that might have otherwise been filtered out rather than providing less-relevant or mismatched impressions that were only surfaced because they were the best of the worst.

For marketers, it means higher-quality, campaign-aligned, readily available supply. Rather than hunting for a scarce audience in a narrow, filtered slice of the funnel, sell-side decisioning clears a path to that audience upstream before the signal gets lost as data passes through the programmatic network, degrading in the process.

“Companies on the bleeding edge of innovation in terms of how to drive performance are able to start participating and working within these transactions to help their customers, whether that be on the publisher side or on the buy side,” McNeeley said. “That changes things because it can be more granular. You’ll get less waste and better performance.”  

This results in more efficient budget allocation, as more of every advertising dollar can go toward working media, helping marketers achieve better results and ultimately improving their ROI. It also provides better campaign outcomes and reduced complexity across the supply chain. More revenue flows to reputable publishers with quality ad experiences, and fewer dollars are spent on made-for-advertising sites (MFAs).

Sell-side decisioning also improves brand safety, as inventory is curated toward proven properties and outcomes, not just reach. Marketers can engage with publisher partners directly, and every impression comes from a publisher’s real ad inventory — essentially building trust by connecting directly to the publisher and screening out brand unsafe impressions. Likewise, marketers can leverage the integrations an SSP has forged across thousands of publishers and hundreds of DSPs to seamlessly activate across any DSP and all supply.

Marketing agency Butler/Till trained its algorithm on performance signals across the entire transaction — including sell-side signals provided by Index Exchange — to provide a brand-safe programmatic strategy for a financial services client. This cut the number of SSPs and suppliers by 90% and domains by 52%, according to Ryan Lammela, group director of channel activation at Butler/Till. 

“Not only does this reduce supply chain complexity and improve transparency, but such simplification and consolidation also improves brand safety by limiting the number and variety of sites the campaign runs across to only the most effective properties,” Lammela said.  

At the end of the day, effective sell-side decisioning includes collaborations between the buy side and the sell side to add an extra layer of customization and brand safety to the programmatic marketplace, according to McNeeley. “Ideally, brands, agencies, buyers and DSPs should be pulling the full weight of what they have access to into their buys in order to get better results,” McNeeley said. “It’s not sell-side decisioning instead of buy-side decisioning. It’s sell-side decisioning with buy-side decisioning.”

In some ways, yes — that can be a helpful way to think about it. The mechanics are different, but the impact is similar: Publishers gain more control and buyers get better access. Plus, the programmatic supply chain becomes more transparent, efficient and outcome-driven.

Header bidding was a turning point in programmatic because it gave publishers more control and transparency by running parallel auctions and accessing more demand. Sell-side decisioning follows a similar logic but takes it a step further by bringing data, measurement and intelligence into an SSP or exchange to be used by publishers, DSPs, brands and agencies.

If header bidding is about improving how impressions are auctioned, sell-side decisioning is about improving which impressions get surfaced and how they’re valued by inserting a layer of intelligence. It enables SSPs to evaluate the likely performance of each impression, apply campaign-specific logic and only send through the opportunities most likely to drive outcomes.

Not at all. In fact, sell-side decisioning is designed to operate within the extremely fast time constraints of programmatic auctions, which means the decisioning typically happens in under 10 milliseconds. This means the logic is applied without adding latency to the transaction.

Because decisions are being made earlier in the supply chain, it can actually reduce processing time and complexity once the process hits the DSP. So by filtering and optimizing inventory before it reaches buyers, sell-side decisioning helps streamline the auction, not slow it down.

Not necessarily. Sell-side decisioning isn’t about increasing prices — it’s about increasing value. By pre-filtering inventory and surfacing only the most relevant, high-quality impressions, buyers are more likely to win auctions that align with their campaign goals, which is likely to improve efficiency and reduce wasted spend.

In many cases, this smarter supply path can lower overall cost per outcome, like CPA or ROAS, by eliminating the need to sift through irrelevant inventory. Buyers aren’t paying more for access — they’re paying for better access.

“There’s not a goal for any additional cost in sell-side decisioning,” McNeeley said. “There are just options, and market options are usually good for the people who are taking advantage of those options — the buy-side customer, if you will.”

Giving buyers more options will benefit publishers as well. When data can be activated for less, marketers will potentially have more money to spend. “So, they’re [sellers] not raising CPMs, but maybe they [marketers] can buy more impressions,” McNeeley said. “The optionality is ultimately a good thing. It’s competition and it will help performance.”

It doesn’t change it — it reinforces it. By applying intelligence on the supply side before a bid is placed, the entire ecosystem becomes more sustainable. Publishers can make relevant impressions ubiquitously available to all of their customers, regardless of the DSP that they use. Buyers get better outcomes, sellers retain more control and the number of wasted or irrelevant impressions shrinks dramatically — reshaping how inventory is valued. 

Smarter sell-side decisioning reduces complexity and noise in the auction process, increases transparency and strengthens the infrastructure that supports programmatic at scale. SSPs, publishers and DSPs can work together more seamlessly, while publishers only benefit financially if transactions increase. 

Meanwhile, the greater the number of platform partners, like data and custom algorithm providers that build upon SSPs’ existing infrastructure, the more value that can be activated for buyers — providing more options at lower prices, with better effectiveness and consistency across DSPs. 

“That starts to make things easier, rather than harder,” McNeeley said. “That’s where sell-side decisioning will help provide efficiencies, transparency and sustainability in the long term.”

Two real-world examples of how sell-side decisioning is being applied innovatively include sell-side curation and agentic decisioning. 

Sell-side curation leverages supply-side signals to give media buyers and platform partners, like data and custom algorithm providers, the ability to create and package their own deals, controlling how they wish to apply their own or other proprietary data and solutions to enhance targeting and performance.

Agentic decisioning enables AI-powered agents to evaluate every impression prior to programmatic auction, weighing price, quality and scale in real time to decide whether that impression should be included in a brand-aligned deal. For example, a brand that prioritizes sustainability can configure its agent to reject any inventory sources above a certain emissions threshold, even if they’re cheaper or offer broader reach.

At the top of the list, marketers and publishers should look for SSPs that offer more than scale. Consider whether an SSP charges fees on data products that are activated on the sell side and if it can provide premium supply integrations. 

Companies without added fees tend to be better partners because they aren’t considering partnerships as purely revenue-generating opportunities, but rather as opportunities for business alignment. Ask if the marketplace has policies against MFAs, which prioritize ad placements over site content, leading to brand safety risks and wasted ad spend. 

Also consider whether an SSP is a technology-focused or a sales-driven company, and if they have the latest tech tools. The right partner should be built for speed, capable of AI-powered curation and transparency in the transactions on a granular level. For marketers, that means a higher signal-to-noise ratio. For publishers, it means tools to activate inventory in smarter, more strategic ways.

Lastly, ask whether an SSP’s business model is aligned with yours. Knowing whom you’re working with and what they’ve said they will do from a business perspective is important. Key questions to ask include: 

• Do they have a good reputation in market? 
• Can they accomplish my business objective? 
• Are they recommended by others? 
• Do they have case studies? 

Proof points like these can make the difference between success and failure in a sell-side decisioning business partnership.

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About Index Exchange

Index Exchange is a global advertising supply-side platform enabling media owners to maximize the value of their content on any screen. We’re a proud industry pioneer with over 20 years of experience connecting leading experience makers with the world’s largest brands to ensure a quality experience for consumers. To learn more, visit: www.indexexchange.com or @indexexchange.