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Reference library · Buying and negotiation
Supply Path Optimization (SPO)
Supply Path Optimization is the practice of mapping every route a buyer can use to reach a given piece of inventory across SSPs, exchanges, and resellers, then routing bids only through the paths with the lowest fees, cleanest ads.txt/sellers.json declarations, and least duplication. It cuts intermediary take rates and reduces exposure to unauthorized resellers and domain spoofing. The output is a pruned, approved list of paths that the buyer's DSP defaults to for that publisher or SSP.
Worked example
A buyer spends €50,000/month on a Polish news site's inventory, routed through 7 SSP paths with take rates from 12% to 38%, averaging 24% combined, so about €12,000/month goes to intermediaries. A path audit against the site's ads.txt shows only 2 of the 7 are authorized direct paths, at 12% and 15%. Cutting to those two paths (13.5% average) drops intermediary cost to about €6,750/month, freeing roughly €5,250/month on the same budget for added reach or a lower effective CPM.
How it is used
Traders run path audits per SSP or per top publisher, cross-referencing ads.txt and sellers.json against the SupplyChain (schain) object to flag resold and duplicate paths, then rank the survivors by take rate, latency, and win rate before setting DSP-level path deals or exclusions. Audits repeat quarterly or when a new SSP relationship is added rather than once, since a path that was clean six months ago can quietly get resold again.
The common mistake
The most common error is pruning purely by take rate; a cheap path that carries most of the fill or is the publisher's preferred route can lose more in win rate and reach than it saves in fees.