How publishers package their own audience segments, declare them in the bidstream with standardized IAB taxonomy IDs, and sell audience without exposing a single user identity — and where the data behind credible SDA segments actually comes from.
Seller Defined Audiences (SDA) is an IAB Tech Lab specification that lets publishers package their own first-party audience segments and declare them in programmatic bid requests using standardized IAB Audience Taxonomy IDs — without exposing any user identity. Released in early 2022 as part of Project Rearc, SDA is the supply side's structural answer to cookieless audience segmentation.
Segments are not free-text labels a publisher invents. They are IDs from the IAB Audience Taxonomy, so “Business Decision Makers” means the same thing from every seller.
Segment IDs travel in the bid request attached to the impression. No cookie sync, no identity graph, no user-level data ever leaves the seller's environment.
The supply-chain transparency stack — sellers.json and the SupplyChain object — tells buyers exactly who declared a segment, attaching trust to a named, auditable seller.
The hard part of SDA is not the plumbing — it is the audience data. A seller needs evidence before it can declare anything credible. This guide walks through the spec end to end, then addresses that data problem directly, because it is where most SDA initiatives stall.
For most of programmatic history, audience was a buy-side product built on cross-site identity. SDA exists because that assumption stopped holding.
Safari and Firefox block third-party cookies by default since 2019–2020; iOS restricts app-level identifiers. Chrome has kept cookies but the blocking browsers alone put roughly 40%+ of traffic beyond reach.
Third-party segment vendors were cookie products end to end. Several major providers scaled down or exited ad data entirely as the signal eroded beneath them.
GDPR, CCPA and successors make cross-site tracking consent-dependent and expensive. Data that never leaves the seller's environment carries structurally less regulatory exposure.
Publishers always had the most defensible audience knowledge — their own readers — but no standardized way to sell it programmatically. Bespoke ad-server keys don't scale across a thousand DSP seats.
SDA transfers responsibility: if cross-site observation is going away, let audience be asserted by the party that still legitimately knows it — the seller with the direct content and reader relationship — and give buyers standardized vocabulary and supply-chain transparency so the assertion can be trusted.
SDA assembles existing IAB Tech Lab standards — a taxonomy, an OpenRTB extension, and the supply-chain transparency layer — into a four-step flow.
The seller assembles evidence: registration data, survey panels, analytics, contextual signals, or licensed content-inferred audience data. The spec does not dictate methodology — only how the result is declared.
Each cohort is expressed as segment IDs from the IAB Audience Taxonomy (v1.1) covering demographics, interests and purchase intent. Standard IDs make segments tradable across every DSP.
Segments travel in OpenRTB's user.data (audience) or site.content.data (content), each with a segtax extension — segtax: 4 for Audience Taxonomy 1.1. No user ID accompanies the declaration.
Buyers verify who declared the segment via sellers.json and SupplyChain, and can consult published transparency documentation. DSPs target, price and report on SDA signals like any other audience.
The name field identifies the asserting party, cross-referenced against sellers.json. Because segtax is explicit, sellers can send multiple signal sets side by side — audience and content taxonomy codes in one request, each unambiguous.
IAB Tech Lab's companion spec supplies the “nutrition label” sellers use to disclose segmentation methodology — data source, recency and derivation — so buyers can distinguish survey-calibrated from declared segments.
What is absent from the flow: cookie syncing, identity graphs, hashed emails, fingerprinting. SDA's privacy posture comes from architecture — the audience assertion is a property of the impression, and the buyer never receives material that identifies a person.
SDA is a chain: it only pays off when every link — from the party that knows the audience to the party spending against it — handles the signal.
The originators. They own the audience relationship, build or license the data, choose the taxonomy IDs, and declare segments — keeping the data premium on their side of the trade.
The carriers. Supply-side platforms pass user.data signals through in bid requests, expose SDA-based packages as Deal IDs, and offer segment management tooling.
The aggregators. Curators assemble SDA-signaled inventory from many sellers into cross-publisher audience packages for scale. See our ad inventory curation guide.
The demand. DSPs parse segtax-coded segments and let buyers bid on them. Buy-side adoption is SDA's bottleneck — which is why transparency and standard IDs matter most.
The spec cannot solve its own data problem: a segment ID is an assertion, and assertions need evidence. Over-declare and buyers' outcome data will disagree; under-invest and there is nothing to declare.
A publisher that labels every impression “Business Decision Makers” because the label prices well will be caught when buyer outcome data disagrees. The discount that follows attaches to the seller's name permanently.
Logged-in registration covers only a fraction of most publishers' traffic. Survey panels are expensive and sparse. Long-tail sections of even large networks have no first-party audience evidence at all.
A mortgage-calculator section is read by mortgage intenders; a cloud blog by senior technical staff. Our audience segmentation engine computes this evidence with banded confidence.
A precomputed domain-level dataset of 102M domains for network-wide planning, and a per-URL real-time API for page-level declaration granularity — matching how SDA is deployed.
Every attribute comes from a controlled vocabulary (v1.0) aligned with IAB Audience Taxonomy 1.1. Mapping to declarable SDA segment IDs is a vocabulary translation, not a research project.
INT.* codes)PI.* codes)Confidence bands guide declaration policy. Declare only high-confidence attributes on guaranteed deals; accept medium-and-above for broader packages; never declare what the evidence does not support. Browse the full vocabulary on the audience segmentation taxonomy page.
A publisher network wants to package its business and enterprise-tech inventory as a Business Decision Makers SDA deal. Step one is evidence: profile the candidate inventory.
{
"input": "https://example-biz-publisher.com/
enterprise-software/",
"audience_profile": {
"demographics": {
"age_brackets": [
{"code": "35_44", "confidence": "high"},
{"code": "45_54", "confidence": "medium"}
],
"income_band": {"code": "upper_middle_income",
"confidence": "medium"}
},
"interests": [
{"code": "INT.business_finance.business",
"confidence": "high"},
{"code": "INT.personal_finance",
"confidence": "low"}
],
"purchase_intent": [
{"code": "PI.software.computer_software",
"confidence": "high"}
],
"b2b": {
"is_b2b": true, "confidence": "high",
"target_roles": ["it_manager", "director"],
"company_size": "201_500"
},
"personas": [
{"persona": "IT Decision Maker",
"source": "deterministic_mapping"}
],
"vocabulary_version": "v1.0"
}
}
The section qualifies: B2B at high confidence, senior roles, enterprise-software intent. The publisher repeats this across the network and admits only inventory clearing the threshold.
// Bid request fragment (segment IDs illustrative) "user": { "data": [{ "name": "example-biz-publisher.com", "segment": [ {"id": "553"}, // interest branch {"id": "1216"} // purchase-intent branch ], "ext": {"segtax": 4} // Audience Taxonomy 1.1 }] }, "source": { "ext": {"schain": { /* verifiable seller chain */ }} }
Qualifying inventory is mapped to Audience Taxonomy 1.1 IDs, declared in user.data with segtax: 4, and exposed to buyers as a Deal ID — “Business Decision Makers, network-wide.”
The publisher shows a per-URL derivation trail — this page, this content, these attributes at these confidence levels — instead of “trust our segment name.” That story is the difference between a premium SDA deal and run-of-network pricing.
Three ways audience reaches a programmatic buyer. They are not mutually exclusive — sophisticated sellers run SDA on top of content-derived evidence.
| Dimension | Seller-defined audiences | Buyer-side (3P) audience data | Contextual / content-based |
|---|---|---|---|
| Who packages | The publisher or seller | Data vendors and DMPs | Either side, from page/domain signals |
| Underlying data | Seller's first-party + content-inferred | Cross-site behavioral observation | Content topics and inferred audience |
| Identity dependence | None — segments describe impressions | Requires cookies or ID graphs | None — describes pages |
| Cookieless coverage | Full, wherever the seller declares | Degrades with blocked cookies | Full — every page on every browser |
| Transaction surface | user.data + segtax; Deal IDs | DSP audience marketplace, pre-bid | Deal IDs, allowlists, pre-bid contextual |
| Standard vocabulary | IAB Audience Taxonomy 1.1 | Vendor-proprietary taxonomies | IAB Content Taxonomy; audience if enriched |
| Transparency | sellers.json, SupplyChain, labels | Historically opaque | Fully explainable from content |
| Main risk | Over-declaration eroding trust | Shrinking signal, regulatory exposure | Coarse if topic-level only |
| Who captures value | The seller | The data vendor | Whoever holds the enrichment |
The diagonal relationship: buyer-side audience data is in structural decline, contextual inference is the evidence layer that scales without identity, and SDA is the standardized rail that lets sellers monetize that evidence. How buyers activate the same signals is covered in cookieless targeting.
Seller Defined Audiences (SDA) is an IAB Tech Lab specification, released in 2022, that lets publishers package their own first-party audience segments and declare them in OpenRTB bid requests using standardized segment IDs from the IAB Audience Taxonomy. Buyers receive a structured audience signal attached to the impression — without any user identity, cookie sync or ID graph.
Through OpenRTB's data objects: audience segments travel in user.data and content signals in site.content.data. Each data block names the asserting party and carries a segtax extension — segtax: 4 for IAB Audience Taxonomy 1.1. Buyers verify the declaration through sellers.json and the SupplyChain object.
No. SDA requires no third-party cookie, device ID or cross-site identifier. Segments are computed inside the seller's environment and declared as properties of the impression. That makes SDA fully functional on Safari, Firefox and iOS — roughly 40%+ of traffic — and independent of whatever Chrome does next.
The IAB Audience Taxonomy, version 1.1, whose three branches cover demographics, interests and purchase intent. Our own audience vocabularies are aligned with Audience Taxonomy 1.1, so content-inferred profiles translate directly into declarable SDA segment IDs. See the IAB Audience Taxonomy guide.
They are complementary layers. SDA is the signaling standard — how a seller declares audience on impressions. Curation is a packaging workflow — assembling inventory from many sellers into a Deal ID. Curated deals frequently use SDA signals as inputs, and cross-publisher curation is how SDA achieves the scale a single publisher cannot offer. See ad inventory curation.
From three sources, usually combined: authenticated first-party data, research panels, and content-inferred audience data with confidence bands. Content inference covers the anonymous and long-tail traffic that first-party data misses, and outputs attributes aligned with IAB Audience Taxonomy 1.1.
Open the interactive demo, paste any page or domain from your network, and see the full content-inferred audience profile — the evidence layer behind a defensible SDA segment.