Consider the current market reality: Publishers now partner with dozens of sell-side technology platforms, yet the vast majority of bid requests go unprocessed due to system congestion. Meanwhile, a handful of major platforms control the majority of open internet investments, leaving agencies trapped in a fragmented ecosystem where volume has replaced value as the primary currency.
The traditional SSP evaluation playbook—built on reach, inventory access, and competitive CPMs—isn't just outdated. It's actively undermining agency success.
Having spent years at the intersection of supply-side technology and buyer needs, I've witnessed this transformation firsthand. The agencies winning today aren't those with the most SSP relationships. They're the ones who've fundamentally rethought what quality supply means in an era of signal degradation, bidstream manipulation, and misaligned incentives.
Here, I’ll examine why 2025 demands a complete rethinking of SSP partnerships, shifting from reach-based relationships to performance-driven alliances:
- The four critical evaluation factors that matter now
- Why legacy SSP relationships systematically fail
- The alternative approach rewriting industry rules
- Practical next steps for agency leaders
The agencies that recognize and act on this shift will capture disproportionate value in 2025. Those that don't will find themselves increasingly marginalized in an ecosystem that no longer rewards volume over value.
The programmatic supply chain is no longer neutral
For years, the industry operated under a foundational assumption: that SSPs were neutral intermediaries, connecting buyers to inventory in an unbiased marketplace. But this assumption is dangerous to maintain in 2025.
Why "more access" no longer equals better outcomes
While publishers have expanded their SSP partnerships to an average of 24.5 platforms (according to the Jounce Media 2025 State of the Open Internet report), this explosion in "access" has created systematic inefficiencies that actively harm campaign performance. Consider the mathematics of modern programmatic:
- Rebroadcasting supply chains now account for 37% of display auctions and 32% of video auctions. These aren't unique inventory opportunities; they're the same impressions being recycled through multiple paths, creating the illusion of scale while generating real costs in processing power and decision fatigue.
- The result? Bidstream congestion that leaves 9 out of 10 bid requests unprocessed, drowning decision-making systems in noise rather than expanding genuine opportunity.
This is the inevitable outcome of a supply chain optimized for volume over value, where SSPs are rewarded for generating bid requests rather than delivering quality outcomes.
💡 Wait, so what is a supply side platform? Supply side platforms (or SSPs) are essentially publishers’ revenue optimization engines that manage how their ad inventory gets sold to advertisers. SSPs connect publishers to demand-side platforms, ad exchanges, and ad networks, allowing them to auction their available ad space to the highest bidder in real-time. The platform handles pricing optimization, fraud prevention, and ensures publishers maximize revenue from their available inventory while maintaining control over which advertisers can access their audiences. Major supply side platform examples and SSP vendors include Google Ad Manager (the largest SSP globally), Amazon Publisher Services, Magnite (formerly Rubicon Project), PubMatic, and OpenX.
The bias problem: When "neutral" platforms pick favorites
Legacy SSPs operate with fundamental conflicts of interest that agencies rarely examine. Many prioritize their own inventory or favor demand partners who offer the highest revenue shares, not the best advertiser outcomes. The industry's focus on win rates over win quality exemplifies this misalignment.
When an SSP boasts about high win rates, what they're really telling you is that they've successfully captured impressions, not that those impressions drove meaningful business results. This volume-centric approach incentivizes SSPs to flood the market with easily winnable, low-quality inventory rather than compete for premium placements that require sophisticated optimization.
The transparency gap compounds the problem. The average ads.txt file now includes over 450 authorized supply paths, a threefold increase since 2020. Yet most agencies have no visibility into which paths their SSPs actually use, what fees are applied at each hop, or how inventory selection decisions are made.
Market behavior reveals the depth of this problem: when 91% of programmatic display spending flows through private marketplaces and programmatic direct deals (growing 13% annually while open exchange spending grows just 3%), it's clear that sophisticated buyers are actively avoiding the "neutral" open auction entirely. They've recognized what many agencies haven't: that more access often means more waste.
The incentive misalignment crisis
Perhaps most troubling is how legacy SSP business models actively work against buyer interests. SSPs generate revenue from transaction volume, not campaign performance. They're paid to process bid requests and facilitate transactions, regardless of whether those transactions drive advertiser ROI.
This creates perverse incentives:
- Auction duplication becomes profitable because it generates more billable transactions
- Quality filters become revenue reducers because they decrease transaction volume
- Performance optimization becomes secondary to inventory access and processing speed
The evidence is everywhere once you know what to look for. The 19% year-over-year increase in Made-for-Advertising supply is the natural result of systems that reward volume over value. When SSPs make money from every transaction regardless of quality, low-quality inventory becomes a feature, not a bug.
Meanwhile, signal integrity continues to deteriorate. ID alignment rates have collapsed to just 31% on Safari compared to 95% on Chrome, yet many SSPs continue to charge the same premiums for "targeted" inventory that may not be targetable at all.
The bottom line: In 2025, treating SSPs as neutral intermediaries is a strategic liability. Agencies that continue to evaluate these partnerships based on inventory access and competitive pricing are optimizing for metrics that no longer correlate with success.
The question isn't whether you have enough SSP relationships. It's whether your SSP relationships are designed to prioritize your outcomes over their transaction volume.
Four critical factors to evaluate SSPs in 2025
The traditional SSP evaluation playbook (focused on reach, inventory access, and competitive CPMs) is counterproductive. In 2025, successful agencies evaluate SSP partnerships based on four fundamentally different criteria that actually correlate with campaign success.
Bid stream integrity: The foundation of trust
The problem: Signal manipulation has become an industry epidemic. Publishers and SSPs routinely misrepresent targeting information, manipulate auction floors, and duplicate user IDs through non-standard matching methods. The result? Agencies are making bidding decisions based on fundamentally unreliable data.
What to look for: SSPs that can demonstrate authentic signal verification, robust fraud filtering, and minimal auction duplication. The goal involves working with partners who actively police signal quality rather than exploit signal ambiguity for revenue generation.
The reality check: When ID alignment rates vary depending on browser, and Made-for-Advertising supply surges YoY, bid stream integrity is existential. SSPs that can't guarantee signal authenticity are essentially asking you to make strategic decisions based on deliberately corrupted data.
Key questions to ask:
- How do you verify the authenticity of video placement signals?
- What percentage of your inventory passes through fraud detection filters?
- How many auction duplicates does the average impression generate in your system?
Supply path efficiency: Eliminating value-destroying intermediaries
The problem: Complex supply chains create multiple failure points where signals degrade, fees accumulate, and quality controls break down. When the average programmatic transaction touches multiple intermediaries, each adding margin while potentially subtracting value, path efficiency becomes a competitive advantage.
What to look for: SSPs that can demonstrate direct publisher relationships, minimal intermediary hops, and transparent fee structures. The goal isn't necessarily the shortest but the most value-preserving path.
The market evidence: Durable supply chains capture 64% of RTB bid requests and 69% of demand side platform (DSP) gross ad spend. This reflects sophisticated buyers gravitating toward efficient, direct relationships that preserve both budget and signal quality.
Key questions to ask:
- What percentage of your inventory comes through direct publisher relationships versus resold auctions?
- How many intermediary hops does the average impression pass through before reaching buyers?
- Can you provide granular visibility into fees at each point in the supply chain?
💡Demand side platform vs supply side platform: What's the difference? A demand side platform (DSP) is technology that allows advertisers and agencies to buy ad inventory programmatically across multiple publishers and ad exchanges. A supply side platform (SSP) serves the opposite function, enabling publishers to sell their ad inventory programmatically by connecting to multiple demand sources and optimizing revenue through automated auctions.
KPI alignment: Outcomes over activity metrics
The problem: Most SSPs optimize for metrics that correlate poorly with business results. Impression delivery, viewability rates, and even click-through rates do not tell you about campaign impact. When SSPs are rewarded for transaction volume rather than advertiser success, this misalignment becomes systematic.
What to look for: SSPs that can demonstrate alignment with your actual business KPIs—whether that's sales lift, customer lifetime value, brand awareness, or other outcome-based metrics. This requires SSPs to move beyond media metrics and engage with campaign effectiveness at the business level.
The strategic shift: The industry's migration toward private marketplaces (91% of programmatic display spending, as mentioned earlier) reflects buyers demanding more control over campaign optimization. SSPs that can't support custom KPI optimization are being systematically avoided by sophisticated buyers.
Key questions to ask:
- How do you optimize campaigns for business outcomes rather than media metrics?
- Can you demonstrate correlation between your inventory performance and advertiser ROI?
- What tools do you provide for custom KPI tracking and optimization?
Transparency: Operational clarity as competitive advantage
The problem: The complexity of modern programmatic supply chains creates opacity that benefits intermediaries at the expense of buyers. When agencies can't see where their budgets are allocated, how inventory is selected, or why certain optimization decisions are made, they lose strategic control over their most important investment.
What to look for: SSPs that provide granular visibility into inventory sources, pricing mechanisms, optimization algorithms, and performance attribution. True transparency goes beyond reporting, it includes explainable decision-making processes and predictable fee structures.
The trust deficit: With ads.txt files now including 450+ authorized supply paths, complexity has exploded while transparency has declined. SSPs that can cut through this complexity with clear, actionable insights create genuine competitive advantage for their agency partners.
Key questions to ask:
- Can you provide real-time visibility into where my budget is being allocated?
- How do your optimization algorithms make inventory selection decisions?
- What percentage of my spend goes to working media versus fees and margins?
The integration challenge
What most agencies miss is that these four factors do not operate independently:
- Bid stream integrity enables supply path efficiency, as clean signals make direct relationships more valuable.
- Supply path efficiency, in turn, supports KPI alignment, since fewer intermediaries mean more budget is available for performance optimization.
- Finally, KPI alignment demands transparency, because you cannot optimize what you cannot measure and understand.
Legacy SSPs typically excel in one or two areas while failing in others. The SSPs winning in 2025 are those that have engineered systems where all four factors reinforce each other, creating compound advantages that traditional evaluation methods can't detect.
The bottom line: These evaluation criteria serve as predictors of campaign success in an ecosystem where traditional advantages have evaporated. Agencies that adopt these frameworks position themselves to capitalize on the structural shifts reshaping programmatic advertising while avoiding the systematic failures of legacy SSP relationships.
Why traditional SSP relationships fall short
The programmatic ecosystem's structural problems run deeper than most agencies realize. After years of observing supply-side technology evolution, the evidence is clear that traditional SSP approaches have become strategic liabilities rather than competitive advantages. Now, let me elaborate.
The supply competition trap
Traditional SSPs remain locked in an outdated competition model, assuming that buyers reward the highest quality inventory with disproportionate budget allocation. However, market behavior tells a different story.
Automated bidding systems increasingly treat supply as a commodity, where auction volume matters more than auction quality. This reality drives SSPs to flood markets with maximum inventory at minimum cost, while sophisticated buyers migrate toward controlled environments that prioritize outcomes over access.
Market value no longer flows to companies that simply aggregate supply—it concentrates among those who control demand. Publishers have responded by embracing sell-side curation and wresting demand control from DSPs, while traditional SSPs clinging to inventory-access models lose relevance.
Signal manipulation as business strategy
When SSPs can’t differentiate through genuine value creation, many resort to technical manipulation as their primary competitive strategy. This includes systematically structuring bid requests to extract maximum DSP demand while obscuring actual inventory quality.
Common manipulation tactics include:
- Floor pricing games that create artificial scarcity
- Placement bundling that obscures individual impression quality
- ID duplication through non-standard matching methods
- Misrepresentation of inventory characteristics
This approach systematically erodes trust across the programmatic ecosystem. When revenue generation takes priority over signal accuracy, the entire market suffers reduced efficiency and effectiveness.
Win rates vs. win quality: The core misalignment
Traditional SSP metrics reveal profound incentive problems. Win rate optimization rewards transaction volume while ignoring advertiser value creation. SSPs achieve impressive win statistics by directing buyers toward easily-captured inventory that sophisticated advertisers systematically avoid.
The market's verdict is clear: The majority of programmatic spending has shifted to private marketplaces and controlled environments. Buyers have abandoned the high-volume, low-quality open auction environment in favor of curated, transparent alternatives where performance can be properly measured and optimized.
The consolidation acceleration
The current market trajectory points toward continued consolidation among platforms that have transcended pure supply-access models. These emerging leaders accumulate market power precisely because they've embraced demand-side thinking and outcome-based optimization.
Traditional SSPs face an existential challenge: competing on supply volume and technical manipulation both represent failing strategies. The market increasingly rewards platforms that facilitate performance and transparency, yet most legacy SSPs lack the structural capabilities to make this transition.
Compounding strategic failures
These problems create a destructive cycle. Volume-driven revenue models encourage auction duplication and signal degradation. This forces DSPs to make faster, less-informed decisions, reducing campaign effectiveness. Poor performance drives buyers toward private marketplaces, further commoditizing open auction inventory and accelerating the decline.
The programmatic landscape shows more dynamism in 2025 than at any point in recent years. However, this dynamism favors platforms built around buyer success rather than transaction volume. Traditional SSPs designed for earlier market conditions find themselves structurally disadvantaged in this transformed environment.
How Smart Supply is rewriting the rules
While traditional SSPs grapple with structural misalignments, a new generation of supply solutions is emerging, built specifically for 2025's programmatic realities. AI Digital’s Smart Supply exemplifies this transformation, demonstrating how buyer-centric architecture can convert traditionally problematic supply relationships into strategic assets that drive measurable business growth.
Eliminating structural bias through design
Traditional SSPs face an impossible task: serving publishers seeking maximum revenue while simultaneously serving buyers seeking maximum value. Smart Supply's architecture resolves this conflict by designing systems explicitly from the buyer's perspective.
No DSP-side bias means optimization decisions align with campaign performance rather than platform economics. When inventory selection operates free from revenue-sharing agreements or platform partnerships, agencies gain access to truly neutral supply selection that prioritizes advertiser outcomes over SSP margins.
This design philosophy extends beyond inventory selection to complete operational transparency. Where legacy SSPs obscure fee structures and selection criteria, buyer-centric systems provide visibility into decision-making processes and cost applications. Agencies can finally make strategic decisions based on performance data rather than vendor promises.
AI-powered selection for outcomes
The philosophical difference between Smart Supply's AI implementation and traditional programmatic optimization reveals itself in results. Legacy systems deploy AI to maximize transaction volume and revenue extraction. Intelligent curation systems use AI to maximize campaign effectiveness and advertiser ROI.
This approach inverts the traditional model entirely. Rather than forcing buyers to defend against low-quality supply, AI-powered systems proactively filter inventory based on performance predictors, fraud indicators, and brand safety signals. Every impression becomes a learning opportunity that improves future selection quality.
Real-time optimization extends beyond static inventory availability to continuous supply recommendation adjustments based on campaign feedback. When systems optimize for downstream business impact rather than media metrics, premium placements that drive genuine results become appropriately valued while high-volume, low-impact inventory gets correctly devalued.
👉 Learn more about the future of programmatic advertising in our dedicated article: Supply-Side Optimization with AI.
Strategic partnership over vendor relationships
Smart Supply's approach recognizes that successful agencies require partners, not vendors. Efficiency without accountability reduces to mere automation. The platform combines operational efficiency through AI-powered optimization with strategic accountability through transparent reporting and explainable decisions.
This partnership model changes how challenges get addressed. Traditional SSPs treat issues as isolated technical problems requiring technical fixes. Strategic partners understand that programmatic challenges usually reflect broader campaign objectives that demand collaborative problem-solving.
The compound advantage
These elements create reinforcing benefits that explain why agencies working with next-generation solutions often achieve performance improvements that traditional optimization couldn't deliver. Buyer-centric design enables superior AI optimization because systems operate without conflicting revenue incentives. Intelligent curation supports outcome-based optimization because higher-quality supply generates more reliable performance signals.
When platforms and agencies share success metrics, the entire optimization framework transforms from inventory access management to strategic campaign enhancement. Agencies gain access to strategies that weren't possible within legacy framework constraints—not just better execution of existing approaches.
Conclusion: What agencies should do next
The transition from traditional SSP relationships to performance-driven supply partnerships isn't just about changing vendors, it's about fundamentally rethinking how agencies create value. The agencies that make this transition strategically will capture disproportionate advantages in 2025 and beyond.
Rethink what "quality" supply really means
Traditional definition: Quality supply meant premium publisher brands, high viewability rates, and competitive CPMs. These metrics optimized for the appearance of quality rather than the reality of performance.
2025 definition: Quality supply means inventory that consistently drives your specific business outcomes through transparent, efficient paths. This might include emerging publishers with engaged audiences, contextually relevant placements that don't rely on problematic targeting signals, or premium inventory accessed through direct relationships rather than auction markup chains.
The shift requires moving beyond surface-level quality indicators toward deeper performance analysis. Instead of asking "Is this a premium publisher?" ask, "Does this inventory consistently drive outcomes for campaigns with similar objectives?" Instead of focusing on viewability percentages, examine correlation between viewability and downstream business impact for your specific use cases.
Start asking deeper questions about SSP relationships
Most agency-SSP conversations focus on inventory access, pricing competitiveness, and technical capabilities. The questions that actually predict partnership success go much deeper:
"What is a supply side platform's primary optimization objective?" If the answer focuses on win rates, impression volume, or revenue maximization rather than advertiser outcomes, you're looking at a traditional model that prioritizes platform success over campaign performance.
"How should you vet SSP vendors for outcome alignment?" Look for evidence of genuine business metric optimization, not just media metric optimization. Can they demonstrate correlation between their inventory performance and your actual KPIs? Do their optimization algorithms consider your business objectives, or just programmatic efficiency metrics?
"What visibility do you provide into optimization decision-making?" The most sophisticated SSPs can explain not just what they optimized, but why specific optimization decisions were made and how those decisions connect to campaign performance. Transparency isn't just reporting—it's explainable methodology.
"How do you handle conflicting interests between publishers and advertisers?" The honest answer reveals whether the SSP has structural mechanisms for prioritizing advertiser success when it conflicts with publisher revenue maximization, or whether they're still trying to serve two masters simultaneously.
The time to act is now
The window for strategic advantage through supply-side innovation is open now, but it won't remain open indefinitely. As more agencies recognize the limitations of traditional SSP relationships and move toward performance-driven alternatives, early-mover advantages will erode.
The agencies that act decisively in 2025 will establish competitive positions that become increasingly difficult to replicate. Those that wait for industry consensus or perfect solutions will find themselves perpetually catching up to more strategically aggressive competitors.
The choice isn't between perfect solutions and imperfect ones; it's between strategic progress and strategic stagnation. After all, the biggest risk isn't making imperfect decisions; it's failing to make strategic decisions at all. The programmatic has changed. The question is whether your SSP evaluation criteria have changed with it.
Want to keep the conversation going?
Feel free to reach out and connect with me at britany.scott@aidigital.com!
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