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IAB Tech Lab drafts rules against duplicate ad bid requests
Publication date: 25.09.2026
In brief
- The Programmatic Governance Council at IAB Tech Lab published voluntary guidance against duplicate bid requests.
- The rules cover bid caching, ad refresh timing and gaps in the supply chain object, schain.
- Comments are open from September 16 to October 16, 2026, and adoption will not be mandatory.
46%of inventory from Tier 1 SSPs reaches buyers through multiple paths at once, according to DataBeat's June 2026 measurement.
When you buy an impression in programmatic, an auction runs behind the scenes, and the seller's server sends bid requests for every single impression. Duplicates among those requests became so common that the industry decided to write rules. PPC Land reports that the Programmatic Governance Council at IAB Tech Lab issued voluntary guidance aimed at bid caching, ad refresh timing and schain gaps.
One ad slot, several requests
Here is the picture in simple terms. One ad slot on a publisher page can reach a buyer by two or three different routes, and each route creates its own request. The buyer pays infrastructure costs for handling all three even though only one impression will run. On average there are 1.31 intermediaries per duplicated path.
The guidance has seven sections. The ones that matter most to an advertiser are in the table.
| Section | What it proposes |
|---|---|
| Bid caching | Keep bids only within their expiration window and only for "materially the same" placements |
| Placement identifiers | One identifier per unique ad slot, no surplus request IDs |
| Ad refresh | Run auctions on the declared refresh interval, with no silent frequent ones |
| Request duplication | Ban exact clones and fan-out, where an array is exploded into separate requests |
The guidance also requires a SupplyChain object in every request, meaning a note on where the request came from, and well-kept ads.txt and sellers.json files. That gap is old: HUMAN Security's November 2023 data showed only 42% of such objects in live bid requests validated.
Who wrote it and why nobody is forced to follow it
The council is co-chaired by Scott Both of Hearst, Huda Kazi of Warner Bros. Discovery, Harry Wilkins of Zynga and Ben Hovaness of Omnicom Media Group. Founding members include Omnicom, WPP, Dentsu, Disney, Amazon Ads, The Trade Desk, Magnite, PubMatic, Yahoo, Raptive and Mediavine. Buyers and sellers sit at the same table, which is genuinely rare.
The rules are voluntary. Nobody will fine or disconnect anyone, so it all rests on the goodwill of the parties. The market is already tackling the problem with its own tools: PubMatic introduced an Excess Inventory Fee in April 2026, $0.001 CPM on volume above daily caps the company does not disclose, and Amazon donated its Dynamic Traffic Engine filter to IAB Tech Lab. Publishers Chegg and Daily Mail have throttled requests since 2025.
Where Ukrainian buyers feel the cost
Directly, not much: Ukrainian companies rarely work with SSPs, and the cost of duplicates is baked into intermediary fees you cannot see on the invoice. But if your display campaigns run through a DSP or agency, there is something to ask about: which placements and which paths your ads actually run through. DataBeat's figures are independent, but PPC Land does not explain how it counted duplicates, so I would treat 46% as an order of magnitude.
I am curious how many intermediaries will read the document before October 16 and what survives once the comments are collected. A fee of a tenth of a cent per thousand impressions looks like small change until you multiply it by US programmatic spend of $200 billion a year.
