Private marketplaces (PMP): how invite-only programmatic deals work

Why PMPs exist

The open exchange has two structural problems. The first is inventory quality: any bid can win any impression, so buyers face MFA sites, low-viewability placements, and brand-safety risk unless they invest heavily in filtering. The second is auction dynamics: when premium publisher inventory mixes with long-tail inventory in the same auction, the publisher's expected price is dragged down by the long-tail clearing price.

PMPs solve both. The publisher's premium inventory is segregated into deal IDs visible only to invited buyers, who pay a higher floor price for the privilege. Inventory quality is enforced at the deal level, not at the impression level. Brand-safety risk drops because the buyer chooses the publisher list directly.

The mechanics: deal IDs, seat IDs, floor prices

The handshake works like this:

1. The publisher (or their SSP) defines a deal: which sites, which placements, which audience segments, which buyers, which floor price, which start and end dates.
2. The SSP issues a deal ID — a string like pmp_vogue_homerun_1234 — and shares it with the buyer.
3. The buyer adds the deal ID to a line item in their DSP. The line item is set to bid only on impressions carrying that deal ID.
4. When an eligible impression is available, the SSP signals the deal ID to the DSP. The DSP submits a bid. If multiple deals are eligible, the highest priority wins per the SSP's prioritization rules.
5. Reporting reconciles between DSP and SSP using the deal ID as the join key.

The four PMP variants

Type	Price	Volume	Auction	Use case
Open-priced PMP	Floor + bid	Best effort	Yes (1st or 2nd price)	Standard quality programmatic
Preferred deal	Fixed	Best effort	No (first look)	First-look access at known price
Programmatic guaranteed (PG)	Fixed	Guaranteed	No	Reserved inventory, programmatic delivery
Curated PMP / Marketplace	Floor + bid	Best effort	Yes	Themed inventory bundles (CTV genres, contextual segments)

What goes into a good PMP negotiation

The deal terms should specify:

• Sites, sections, and ad units. Include the URL patterns; "Vogue.com/fashion/*" not "Vogue.com." The publisher's premium pages and their default pages have very different audience profiles.
• Floor price. Usually 50-200% above the publisher's open-exchange clearing price for the same inventory. Anchor against the SSP's marketplace insights.
• Audience constraints. If the deal is for the publisher's first-party audience (e.g., "logged-in subscribers"), name the segment. If you're applying your own audience, document it.
• Viewability and IVT guarantees. Some PMPs include a viewability SLA (e.g., 75% MRC-viewable); below the SLA, the publisher credits make-goods or refunds the underdelivery.
• Brand-safety thresholds. The buyer's pre-bid filters apply (DV, IAS, Moat) and the publisher attests to their content safety controls.
• Deal priority and exclusivity. Is this an exclusive deal (one buyer only) or shared? Is it first-look (priority over open-exchange bids at any price) or competitive (still competes with other deals)?

Common PMP failure modes

No throttling. Buyers add a deal ID to a high-budget line item and the DSP burns the day's budget in the first few hours. Set pacing controls and frequency caps inside the deal, not just at the line-item level.

Floor too high. If the deal's floor price is above what the DSP's bidding algorithm wants to pay, the deal won't deliver. Renegotiate the floor or accept the under-delivery.

Targeting mismatch. The buyer applies their own audience filter on top of a publisher audience deal, intersecting two narrow audiences into near-zero. If the publisher segment is the entire selling premise, don't layer additional targeting.

Reconciliation gaps. DSP-reported delivery and SSP-reported delivery can diverge by 1-5% due to discrepancies in how each system counts. Above 5%, escalate to the SSP. Track this metric monthly.

When PMPs don't make sense

For small budgets (under $5K/month on a given publisher), PMPs aren't worth the trafficking overhead. Run open-exchange with inclusion lists instead. For inventory that's available abundantly on the open exchange at low prices (long-tail display, retargeting), the PMP premium isn't justified. PMPs make sense when the premium is paying for something — premium inventory, premium audience, or brand-safety certainty.

What's the difference between a PMP deal ID and a seat ID?

A deal ID identifies a specific deal between one publisher and one (or a few) buyers. A seat ID identifies the buyer's account in the SSP or DSP. The SSP uses the seat ID to know which buyer the bid is coming from and whether they're authorized for the deal. Deal ID = the deal; seat ID = the buyer.

Can I run a PMP without an agency?

Yes. Many publishers have programmatic sales teams that negotiate directly with advertisers. The DSP-side work (adding the deal ID to a line item) is straightforward. The negotiation and reconciliation overhead is the bigger commitment.

Does a PMP guarantee viewability?

Not by default. You can negotiate a viewability SLA into the deal terms, but it's not a standard inclusion. Without an SLA, the deal-level viewability is whatever the inventory naturally delivers — often higher than open-exchange but not guaranteed.

Why isn't my PMP delivering?

The top three reasons: (1) floor price is too high for current demand, (2) audience filters on top of the deal narrow it to near-zero, (3) the deal ID isn't activated correctly on the DSP line item. Check each in order. Most under-delivery is reason 2.

Do PMPs work for CTV?

Heavily. CTV is mostly transacted via PMP and PG because the inventory is premium, the deals are large, and the audience targeting is household-level rather than user-level. The open exchange exists for CTV but represents the long tail.

What's a curated marketplace?

A curated marketplace is a PMP packaging inventory from many publishers around a theme — "luxury auto enthusiasts," "sustainability content," "CTV sports inventory." The curator (usually an SSP, data provider, or agency) negotiates with publishers, builds the audience layer, and resells the packaged deal to buyers. Curated marketplaces are growing fast in 2026 as ad-tech consolidates around themed supply paths.

Operating checklist

1. Match the buy type to the business goal — guarantee, audience, or efficiency.
2. Confirm inventory access requirements before negotiating price.
3. Set viewability floors and frequency caps inside the deal terms.
4. Test with one publisher before committing to a multi-publisher PMP.
5. Review pacing daily for the first two weeks of any guaranteed buy.
6. Reconcile DSP-side delivery to publisher-side delivery weekly.
7. Document deal IDs and seat IDs in a runbook your future self can read.