Glossary
What is Supply path optimisation (SPO)?
Also called: SPO, supply path optimization
Supply path optimisation (SPO) is buyers keeping only their best routes to a publisher's inventory and cutting duplicate, costly or unclear paths.
हिंदी में पढ़ेंOne impression can reach a DSP through several SSPs and resellers. Each hop can take a fee, and the buyer may get several bid requests for one ad and end up bidding against itself. With supply path optimisation, DSPs and agencies score each path and keep the shortest, cheapest and most transparent ones.
Each DSP’s scoring model is its own, but the questions are similar. Is your ads.txt line DIRECT? Does the SSP’s sellers.json list you as the publisher? Is the schain complete? How big is the fee? One industry analysis, reported by AdExchanger in June 2026, found the typical publisher sells through more than 25 SSPs, which gives buyers plenty of paths to cut.
SPO is done by buyers, but publishers feel it. If a buyer reached you only through a path it drops, that spend shrinks. Direct relationships, matching sellers.json entries and a short, accurate ads.txt make your paths easier to keep.
Example
One impression on news.example reaches a DSP through 4 SSPs: 4 bid requests for 1 ad. Paths A and B are direct and cheap; C and D run through resellers. The DSP keeps A and B and drops C and D, so it now sees 2 requests instead of 4. If a buyer reached you only through C, that spend stops.
Why it matters to publishers
Paths that look indirect or unclear are the first to be cut. Making sure each DIRECT line matches a PUBLISHER entry in sellers.json helps keep you on buyers' preferred routes.