What is Supply Path Optimization (SPO)?

Also known as: SPO

Quick definition

Supply path optimization is the practice of buyers choosing the fewest, cheapest and most transparent routes to the same publisher inventory, cutting redundant resellers so more of the media budget reaches the publisher.

Key points

Inputs: ads.txt, sellers.json, schain, take rates, win rates and IVT rates per path.
Outcomes: Fewer SSP partners, direct paths and curated deals.

Benefits

Lower fees and less duplicate bidding
Better transparency and fraud protection

Trade-offs

Can concentrate the market in a few large SSPs
Smaller publishers may lose demand

FAQ

Is SPO the same as curation?

No. SPO selects paths; curation packages inventory and data into deals. They are often combined.

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Official sources

IAB Tech Lab – Supply chain transparency

Last reviewed 2026-10-27. Explanations are written by AdTech Radar; consult the official specification for implementation.

Find companies

Browse Directory companies working on Supply Path Optimization (SPO).

Related terms

ads.txt & app-ads.txt
ads.txt (for websites) and app-ads.txt (for apps and CTV) are public text files hosted by a publisher that list every ad system and account ID authorized to sell its inventory, letting buyers reject unauthorized resellers and domain spoofing.
sellers.json & SupplyChain Object
sellers.json is a file published by an SSP or exchange that discloses the identity of each seller account it represents, while the SupplyChain object in the bid request records every hop the impression passed through; together with ads.txt they let buyers verify the full path from publisher to DSP.
Take Rate
Take rate is the percentage of advertiser spend that an ad tech intermediary keeps as its fee; in programmatic chains, several DSP and SSP take rates stack, so only part of the original budget reaches the publisher.
Header Bidding
Header bidding is a technique where a publisher offers each impression to multiple SSPs and exchanges simultaneously before calling its ad server, so demand competes on price at once instead of in a sequential waterfall.