What Is Supply-Path Optimization (SPO)?
Supply-path optimization (SPO) is often compared to a courier service. Just as a courier has to find the best route to a destination — saving time and money for all parties — SPO aims to help advertisers find the most efficient route to their desired ad inventory.
This guide explains what supply-path optimization is, where it comes from, why it matters, and how to implement it effectively.
What Is Supply-Path Optimization (SPO)?
Supply-path optimization is the process of finding the shortest and most profitable path to ad inventory for demand-side platforms. DSPs use real-time algorithms to set bids along the shortest and most effective paths to the impressions they want to buy — and those algorithms are what constitute SPO. The results include improving business processes by replacing unprofitable bids with more optimal ones, while simultaneously allowing supply partners (SSPs and publishers) to receive higher ad revenue.
But there is more to this process than simply trimming the supply chain.
Why Advertisers and DSPs Should Adopt SPO
The widespread adoption of header bidding brought many benefits, but it also introduced bid duplication. During header bidding auctions, advertisers and agencies (via DSPs) began bidding on multiple ad exchanges simultaneously to improve their chances of winning the right impression. As header bidding grew in popularity, the number of ad exchanges participating in these auctions increased — and many media buyers started encountering a familiar problem: intermediaries selling the same inventory across different ad exchanges.
SPO comes down to recognizing how many intermediaries exist between the DSP and the publisher, how many fees those intermediaries charge, what their maximum auction timeout is, and what their relationship is to the publisher (i.e., direct or reseller). Optimization strategies differ across platforms — some aim to identify the most relevant bid, while others focus exclusively on trusted partners in the supply chain.
In general, SPO helps identify duplicated auctions so DSPs can avoid them. It also surfaces the most significant factors that make an auction profitable for the bidder, helping both ends of the supply chain reach better outcomes.
How Supply-Path Optimization Works
To apply SPO, advertisers first need to decide which strategies to adopt, since there are many approaches available and SPO can be applied across different areas of the digital supply chain.
To reclaim control and optimize the path to publishers, media buyers can:
- Consolidate the number of SSPs and ad exchanges they work with, limiting activity to a select set of strategic partners.
- Stick to bids that carry the highest chance of winning.
- Stop buying from SSPs that do not allow DSPs to participate in second-price auctions.
- Cut off long-tail SSPs (e.g., resellers).
- Prioritize sellers who offer more exclusive inventory.
The guiding principle is straightforward: in any auction, a given supply link must bring unique value. That way, every dollar spent on programmatic advertising remains traceable and as impactful as possible.
The Benefits of Supply-Path Optimization
SPO benefits extend well beyond advertisers. The entire optimization process helps all parties in the digital supply chain: advertisers, AdTech companies, agencies, and publishers.
Optimizing advertising buying and selling processes — like optimizing a delivery service — takes some initial effort, but the result is a faster, cheaper, and more reliable operation. SPO helps optimize media budgets, build trustworthy supplier partnerships, increase supply chain transparency, and improve campaign performance through better data and insights. In short, the benefits touch revenue, business relationships, and analytics.
Economic Control
Fees under control. One of the first benefits of SPO is visibility into what ad spend is actually going toward. Discrepancies between numbers reported by SSPs and those reported by a DSP are common, and long-tail SSPs often go unscrutinized. Analyzing and pruning partners produces a clearer picture of what is being paid and why.
Bid shading. Bid shading is an algorithm that analyzes historical bid data to help advertisers pay the lowest possible price for an impression during first-price auctions. Based on the past price of an impression, the ad position, and at what price bids were lost, the algorithm suggests an optimized rate for impressions in current auctions. Bid shading minimizes the risk of overpaying in first-price auction environments.
It is worth noting that bid shading is not universally beneficial — for publishers, it typically results in lower ad revenue.
Revenue Opportunities
Working with trusted partners who offer access to quality inventory translates to more revenue opportunities for all sides. For advertisers, reducing the number of partners means fewer duplicated fees — impressions aren't charged through multiple intermediary layers. For AdTech companies, partnering selectively with quality suppliers creates an opportunity to attract more valuable clients and reinvest savings from removing shady intermediaries into product development.
Valuable Insights
SPO creates opportunities to collect detailed data from the SSPs and ad exchanges involved in a given campaign. This data surfaces specifics about individual auctions — whether bids are timing out, whether auctions are first-price or second-price, and so on.
Collecting this data from multiple SSPs and ad exchanges is, however, a resource-intensive operation. Data acquisition, processing, and storage all carry real costs. Building dedicated reporting infrastructure to present this data clearly is an important part of making SPO actionable.
Arbitrage Discovery
In May 2017, the IAB Tech Lab released the ads.txt standard (Authorized Digital Sellers) to help advertisers and DSPs recognize certain forms of ad fraud — notably domain spoofing and inventory arbitrage.
Domain spoofing tricks programmatic advertising platforms into believing an ad will appear on a legitimate site (e.g., newyorktimes.com) when it will actually appear on a different, lower-quality site. Inventory arbitrage involves buying impressions, repackaging them, and reselling them at a higher price.
Publishers and platforms that implement ads.txt files in their root domains can identify unauthorized resellers of a publisher's inventory and exclude them from the supply chain.
Supply Chain Visibility
Getting visibility into a supply chain with many intermediaries is inherently difficult. Falling victim to fraudulent behaviour, wasting money on fees, and losing bids unnecessarily — these are problems that tend to surface and worsen when the supply chain is long and opaque. A shorter, better-understood chain improves effectiveness across the board.
As in logistics, visibility is a core enabler. Insight into every stage of the process reveals not just the services being paid for, but the nature of each supplier relationship.
In programmatic advertising, a buyer's supply chain is only as good as their worst SSP. Optimization is most effective when ad spend is concentrated on preferred, vetted partners.
SPO Benefits for Advertisers
- Reduced bid duplication. One of the primary advantages of SPO is eliminating duplicated bids, making media buying more transparent and efficient.
- Insights into the supply chain. SPO surfaces information about which SSPs and ad exchanges are supplying inventory, what impressions actually cost, and where inefficiencies lie. This data enables better optimization and stronger business decisions.
- Brand safety. Ads appearing on inappropriate pages remain a real problem for advertisers. SPO mechanisms allow for the exclusion of suspicious suppliers that don't meet brand safety criteria.
- Greater transparency. Simplifying the supply chain makes each stage — from auction participation to final impression delivery — more legible, revealing both the strengths and weaknesses of each business relationship.
SPO Benefits for Publishers
The benefits flowing to advertisers have downstream effects on publishers as well. In AdTech, the supply chain is interconnected, and improvements on the demand side tend to lift outcomes on the supply side.
- More direct paths to advertisers. Intermediaries that don't add value will be removed from the delivery path, meaning publishers offering premium inventory receive more direct access to advertiser budgets and, consequently, more ad revenue.
- More competitive positioning. Publishers who care about audience quality and buyer relationships are more competitive under SPO and will attract more ad dollars.
- Market-wide quality improvements. SPO creates pressure on low-quality publishers and resellers to raise their standards or lose access to demand — which gradually improves the overall quality of the market.
How to Implement SPO
SPO is a continuous, iterative activity. The implementation steps outlined here provide a practical framework for getting started and maintaining momentum.
1. Internal Assessment
The first step is understanding what matters most to the business and what is driving (or hindering) success. Calculating ad spend across SSPs and publishers is essential. Key questions to address:
- How many SSPs and ad exchanges are currently used to buy inventory?
- Where are impressions actually coming from?
- How many intermediaries are involved, and what fees are being paid?
2. SSP Evaluation
Before contacting current partners, it's important to define the strategy that will guide evaluation. Evaluation criteria should flow directly from strategic priorities. The differences between SSPs — in terms of auction mechanics, fee structures, and publisher relationships — also help inform a standardized Request for Information (RFI) process.
3. SSP Consolidation and Testing
Most DSPs allow SSPs to be toggled on and off, or for preferred SSPs to be designated. The third step is to design comprehensive test scenarios covering the SSPs and ad exchanges under evaluation — looking for issues related to campaign performance and ensuring that integrations are functioning properly.
4. Ongoing Optimization
Optimization doesn't end after the initial consolidation. The supply chain should be re-evaluated regularly — preferably several times a year — measuring delivery paths against the current purchasing strategy. Both the advertising industry and the companies operating within it evolve continuously, so SPO strategies should evolve with them.
Summary
Supply-path optimization may appear on the surface to benefit only advertisers, but it creates value across the entire programmatic supply chain. SPO algorithms adapt to the programmatic strategy a buyer has defined — but the foundational step is always an honest assessment of the current state. From there, a clear strategy can be developed, applied, and refined over time for measurable gains on both the buy side and the sell side.