The supply path audit: a working checklist.
A supply path audit traces every intermediary between your DSP and the publisher, prices each hop, and removes the ones that can't justify their fee. Done properly, it is a reconciliation exercise — four data sources checked against each other — not a procurement vendetta. This is the checklist we work through.
Why audit at all.
Because the numbers say you should. The ISBA/PwC supply chain studies found that in 2020 only 51p of every programmatic pound reached a publisher, with 15% untraceable entirely; by the 2022 follow-up — after the industry started auditing — publisher share rose to 65% and the "unknown delta" fell to 3%. Scrutiny works. The ANA's Q1 2026 Transparency Benchmark still puts the share of programmatic spend that is fraud-free, viewable, measurable, and MFA-free at just 43.3%. The gap between those who audit and those who don't is widening, not closing.
The checklist.
Inventory every path you buy through
Pull path-level reports from your DSP, including the SupplyChain (schain) object. You want a complete list of exchange → reseller → publisher routes, with spend per route. If your DSP can't produce this, that is finding number one.
Secure log-level data access
Aggregated dashboards hide exactly what you're looking for. Negotiate log-level or bid-level data into your platform agreements. The audit's depth is capped by the granularity of the data you can see.
Price every hop
Map declared take rates for each intermediary on each path: DSP fee, SSP fee, reseller margins, data and verification costs. Sum them per path. Paths to the same publisher can differ by double-digit percentage points.
Reconcile against ads.txt and sellers.json
For each seller in your paths, check the publisher's ads.txt entry (DIRECT vs RESELLER) and the exchange's sellers.json declaration (PUBLISHER vs INTERMEDIARY). Undeclared or mismatched sellers get cut first — no discussion needed.
Set a hop budget
Decide the maximum number of intermediaries you'll tolerate per impression — most disciplined buyers land at one or two. Every reseller beyond the first must demonstrate unique supply you can't reach more directly.
Screen for made-for-advertising inventory
Jounce Media classifies roughly 21% of open-web impressions as MFA, and AI-generated content has accelerated new MFA domains 38% year over year. Apply an MFA classification list to your path data and quantify your exposure before deciding which paths stay.
Find duplicate routes to the same supply
When five paths reach the same publisher, you are bidding against yourself and paying five different toll booths for one road. Keep the cheapest reliable route; cut the rest.
Verify fees against contracts
Compare observed take rates to your rate cards. Our standing rule: if a fee can't be explained in one sentence, it doesn't get paid. Unexplained deltas are negotiation leverage at minimum, recovered spend at best.
Cut, then prove it with a holdout
Don't argue about reach hypothetically. Keep the cut paths alive for a small control slice and compare reach, CPMs, and outcomes after 30 days. In our experience the surviving paths absorb the spend at equal or better efficiency.
Make it quarterly
Paths re-grow. Resellers reappear under new seller IDs, and MFA domains regenerate faster than they're classified. A supply path audit is a discipline, not a project — book it quarterly alongside the ANA benchmark releases.
Questions buyers actually ask.
How long does a supply path audit take?
With log-level access in place, two to four weeks for a single DSP seat: a week to assemble path and fee data, one to two to reconcile, and a week to agree the cuts. Without log-level access, add the time to negotiate it — which is itself a finding.
What data do I need?
Four sources: DSP path-level/log-level reports including schain, each exchange's sellers.json, the publishers' ads.txt files, and your contracts or rate cards. The audit is the reconciliation of these four.
Will cutting paths hurt my reach?
Rarely, and you can measure it instead of debating it. Most publishers are reachable via several routes; cutting duplicates shifts spend to surviving paths. Confirm with a 30-day holdout.
Is this only worth it for big advertisers?
No — the waste is proportional. A third of spend lost to the chain is a third whether you spend $100K or $100M. Smaller buyers usually have simpler paths, which makes the audit faster.
Bring your media plan. We'll bring questions.
Talk to a strategist →Sources: ISBA/PwC Programmatic Supply Chain Transparency Studies (2020, 2022); ANA Programmatic Transparency Benchmark, Q1 2026; Jounce Media MFA classification data; IAB Europe Guide to Supply Path Optimisation. Figures as published by each body; updated June 2026.