What is Supply Path Optimization (SPO)?
Supply path optimization (SPO) is the buyer-side practice of reviewing the different routes through which the same ad inventory is offered, then concentrating spend on the paths that are most direct, transparent, efficient and well performing.
Also known as: SPO
How it works
In programmatic buying, one ad impression can reach a buyer through several routes. A publisher might work with a few SSPs directly, authorize some resellers, and run header bidding so that all of them bid at once. Each of those partners can pass the same impression to the same DSP. From the buyer's seat, that looks like several chances to buy one thing, each with different fees and different levels of trust.
SPO is the process of sorting through those routes. A buyer, or the DSP on its behalf, reviews which sellers and paths deliver the inventory it wants, then favours some and drops others. The goal is to pay less to intermediaries, avoid duplicate bidding against itself and reduce exposure to unauthorized or low-quality supply.
What signals does SPO rely on?
Three IAB Tech Lab standards give buyers most of the raw material:
- ads.txt shows whether a seller account is authorized by the publisher and whether it is listed as DIRECT (controlled by the publisher) or RESELLER (ads.txt 1.1 specification).
- sellers.json lets buyers look up who sits behind each seller account (IAB Tech Lab).
- The SupplyChain object lists every party that handled a specific bid request. Its specification says it is meant to help buyers see all parties selling or reselling an impression and to favour more direct purchases (SupplyChain object specification).
Buyers combine these with their own data, such as fees, win rates, viewability, invalid traffic rates and campaign results, to decide which paths earn their spend.
Why it matters
SPO is a buyer's practice, but its effects land on publishers. If a buyer trims its list of preferred paths and a publisher's inventory only appears through routes that were cut, that buyer's demand quietly disappears. Publishers who keep ads.txt accurate, work with partners whose sellers.json entries are clear, and offer direct or curated deal routes give buyers fewer reasons to look elsewhere.
Example
Example (illustrative)
An agency notices that its DSP receives bid requests for the same sports site from five different sellers. Two are listed as DIRECT in the site's ads.txt, two are resellers and one is not listed at all. The agency stops buying through the unlisted seller, keeps one reseller that brings unique video inventory, and moves most of its spend to the two direct paths and a private deal with the publisher.
IncrementX perspective
SPO rewards inventory that is easy to verify and easy to reach. Representation helps on both counts: clear authorization, sensible partner choices and deal routes that buyers can activate directly. Through its Demand Marketplace and Curated Deals, IncrementX gives buyers defined routes to represented inventory, such as PMP and programmatic guaranteed deals. The seller-side counterpart of this practice is demand path optimization.