What does open exchange programmatic mean for site quality?
Part of Programmatic media planning
The short answer
Open exchange programmatic is buying impressions in an exchange's open auction, where any admitted buyer can bid on any site the exchange sells. Because any seller the exchange admits can take part, site quality varies. Buyers govern it with an inclusion list, authorized seller checks, supply chain rules, suitability settings and a served domain review after launch.
Key takeaways
- On the open exchange, any site an exchange sells is eligible unless a buyer's own rules remove it.
- Among the ANA's benchmark participants, private marketplaces held over 92 percent of median spend in Q4 2025, so open buying is now the smaller, governed share.
- No single control makes open exchange buying safe; inclusion lists, seller checks and supply chain rules each catch different problems.
- The open exchange still reaches independent and small publishers that offer no deals, which is a reason to govern it rather than abandon it.
What does buying on the open exchange mean?
Definition
- Open exchange
- The open auction of an ad exchange or sell side platform, in which any buyer the exchange admits can bid on any impression it offers, with no deal agreed in advance. Also called the open auction, open marketplace or open RTB.
In the OpenRTB 2.6 specification (opens in a new tab), the difference shows up in one field. A bid request's private_auction value of 0 means "all bids are accepted", while 1 means "bids are restricted to the deals specified and the terms thereof." When an impression is offered with no deal, or with deals that still accept all bids, it is open exchange inventory.
That openness is both the appeal and the risk. A buyer can reach thousands of publishers without negotiating with any of them, including small sites that never set up deals. The same openness lets any seller the exchange accepts offer impressions, whatever the site behind them looks like. The programmatic media planning hub covers the plan as a whole; this page is about governing the open part of it.
How much programmatic spend still runs on the open exchange?
The ANA's benchmark participants now buy mainly through deals. The ANA's Q4 2025 Programmatic Transparency Benchmark (opens in a new tab), released February 25, 2026 and the latest public release to report the share, found that private marketplaces accounted for over 92 percent of median spend across environments and 100 percent of CTV transactions among its participants. The open exchange did not disappear in that data; it became the smaller part of the budget.
Why does site quality vary more on the open exchange?
Several things that a deal settles in advance stay open in the open auction, and each one is a quality risk.
- Any admitted seller can offer impressions. The exchange decides who may sell; the buyer decides nothing unless it brings its own rules.
- Sellers declare the site. The domain in a bid request is written by the seller, and IAB Tech Lab built ads.txt (opens in a new tab) to make it harder for bad actors to profit from selling counterfeit inventory.
- Chains can be long. One impression can pass through several resellers, and the SupplyChain object (opens in a new tab) exists so buyers can see all parties selling or reselling a given bid request.
- Made-for-advertising sites compete for the same bids. Among the ANA's benchmark participants, MFA exposure increased to 1.1 percent in Q1 2026 (opens in a new tab) after remaining between 0.4 and 0.6 percent throughout 2025, with AI slop named as an emerging subtype.
The open exchange also carries real strengths. Some independent and local publishers sell only through it, and a buyer who leaves it entirely can lose reach among exactly the specialist readers a contextual brief wants. The fair publisher planning guide covers how to keep those sites in a plan without lowering the bar.
Which controls do buyers use to govern open exchange buying?
Each control catches a different failure. A buyer who relies on one of them alone can discover the gap in a placement report.
| Control | What it catches | Where it falls short |
|---|---|---|
| Inclusion list | Everything not chosen in advance; only reviewed sites can run | Limits scale, and needs upkeep as sites change |
| Exclusion list | Known bad domains across every campaign in the account | Only blocks sites someone has already found |
| Authorized sellers only | Impressions from sellers the site's ads.txt does not name | Says nothing about the content or the ad load |
| Seller type preference | Paths where sellers.json marks the account as an intermediary rather than the publisher | Can remove legitimate sites that rely on resellers |
| Complete supply chain | Requests whose chain does not reach back to the inventory owner | Depends on every node passing accurate data |
| Platform suitability settings | Content the platform classifies as sensitive | Google, for one, says it can't guarantee all related content will be excluded |
| MFA review before listing | Sites built to resell bought traffic | Needs page level review that takes time per site |
Definition
- Complete supply chain
- In the SupplyChain object, complete is a flag indicating whether the chain contains all nodes involved in the transaction leading back to the owner of the site, app or other medium, where 0 means no and 1 means yes.
The seller type rule needs particular care. The sellers.json specification (opens in a new tab) says PUBLISHER means the inventory is on a site, app or other medium owned by the named entity and the advertising system pays them directly, while INTERMEDIARY means it is not owned by the named entity or the advertising system does not pay them directly. An intermediary path is a reason to look, not proof of a problem.
When is the open exchange the right route, and when is a deal better?
| Situation | Governed open exchange line | Deal |
|---|---|---|
| Listed sites offer no deals | Can be the only way to buy them | Not available unless a curated deal covers them |
| Client needs set prices or guaranteed volume | Price moves with each auction | Price or volume can be agreed in advance |
| Short test of new sites | Quick to set up with a list and a small budget | Setup time may outlast the test |
| Strict control of which seller sells | Depends on the buyer's seller rules being set correctly | The deal fixes the seller and terms |
| Large list across many publishers | One line item can carry the list | A curated deal can package the list on one exchange |
How does PlacementGraph help govern open exchange site lists?
What does a governed open exchange plan look like?
Fictional example
A Nashville moving company in Tennessee and Kentucky
A fictional Nashville household moving company wants display ads in Tennessee and Kentucky during the summer moving season, in English, beside relocation guides, neighborhood stories and home buying coverage. Few of the local and specialist sites on its list offer deals, so the desk plans an open exchange line item restricted to the list.
Before launch the planner sets the line to authorized sellers only, checks each site's ads.txt against the exchanges the desk buys on, and notes three neighborhood blogs sold only through resellers. They stay on the list with that note, because their articles fit and their sellers are authorized. A recipe site that ranked for moving checklists fails the MFA review for slideshow pages and heavy refreshing ads, and is left off.
Two regional news publishers do offer private auctions, so those two sites move into deals and come off the open line, avoiding a duplicate bid path. After the first week, the planner reads the served domain report against the approved list, finds every domain accounted for, and files the check with the list version.
What should an open exchange governance checklist include?
Before an open exchange line goes live
- The line is restricted to an approved inclusion list, or the client has accepted broader delivery in writing.
- The account exclusion list is attached and current.
- Only sellers named in each site's ads.txt can win, and the setting is confirmed in the buying platform.
- Reseller only sites are flagged with a note, not removed by default.
- Any supply chain rule, such as requiring a complete chain, is written down with its expected effect on scale.
- Every listed site passed an MFA and page quality review before it joined the list.
- Sites also bought through a deal are removed from the open line to avoid bidding twice.
- A served domain review is scheduled for the first week, with an owner.
Frequently asked questions
Is the open exchange the same as the open web?
No. The open web refers to websites outside large closed platforms, while the open exchange is a way of buying: the open auction with no deal attached. Open web sites can be bought through the open exchange or through deals, and some exchanges also sell app and video inventory in the open auction.
Can the same site list be used on the open exchange and in a deal?
Yes, but split it deliberately. If a site is in a deal and also on an open exchange line, the campaign can bid on it twice through different paths. Decide which route each site belongs to, and record it beside the site so the next version keeps the split.
Does requiring a complete supply chain remove fraud?
It removes one kind of uncertainty. A complete flag says the chain contains every node back to the inventory owner, which helps a buyer see who handled the impression. It does not judge the site's content, ad load or audience, and it depends on each node passing accurate data, so it works alongside the other checks.
Why would a planner keep the open exchange in a quality focused plan?
Because some of the best fitting sites for a specialist brief are small publishers that sell only in the open auction. A governed open exchange line, restricted to reviewed sites with authorized sellers, keeps them reachable. Dropping the route entirely can concentrate the plan on large publishers that run deals.
Sources
- OpenRTB 2.6 specification (opens in a new tab)IAB Tech Lab on GitHub
- ANA Q4 2025 Programmatic Transparency Benchmark Shows Media Quality Is Now Driving Measurable Performance Outcomes (opens in a new tab)ANA, February 25, 2026
- ANA Programmatic Transparency Benchmark (Q1 2026) (opens in a new tab)ANA, May 27, 2026
- ads.txt (Authorized Digital Sellers) (opens in a new tab)IAB Tech Lab
- SupplyChain object (opens in a new tab)IAB Tech Lab on GitHub
- sellers.json specification (opens in a new tab)IAB Tech Lab on GitHub
Researched and written by PlacementGraph Research. Read how we research, source and update these pages. Corrections: diana@placementgraph.com.