automation

Antitrust Shockwaves in Ad Auctions: A Seller-Side Playbook for the Post-Google Lawsuit Era

"Seller ID in bid request must match sellers.json and ads.txt"

Antitrust Shockwaves in Ad Auctions: A Seller-Side Playbook for the Post-Google Lawsuit Era

Antitrust Shockwaves in Ad Auctions: A Seller-Side Playbook for the Post-Google Lawsuit Era

Antitrust risk is no longer a theoretical backdrop to programmatic. With a US federal court finding Google maintained illegal monopolies across parts of the ad tech stack and a remedies phase underway, the center of gravity in ad auctions is shifting toward neutral design, forced interoperability, and verifiable transparency. For sellers, this will open distribution routes, change power dynamics, and accelerate due diligence expectations on the supply side. It will also create execution risk for any publisher or SSP whose stack relies on opaque routing or one-sided commercial constructs that do not age well under a compliance spotlight. This thought piece offers a pragmatic playbook for supply-side leaders. It blends product strategy, technical architecture, and commercial governance to help you anticipate likely remedies, defend revenue in the short term, and build compounding advantage in a market that will prize trust, optionality, and measurable fairness. If you are a Red Volcano customer or follower, you know our bias: more observable supply chains, better identity hygiene, and deeper multi-surface intelligence across web, app, and CTV. That bias is now the direction of travel for regulators and enterprise buyers alike. Let’s turn this moment into momentum.

Where We Are Now: Why This Matters

In April 2025, a US federal court concluded that Google unlawfully maintained monopolies in publisher ad servers and ad exchanges for open-web display. The advertiser network count was more mixed, but the core supply pipes were judged to be monopolized. Remedy discussions have included structural divestiture and conduct remedies, with closing arguments on remedies happening through spring and summer 2025 and the government seeking divestiture of ad tech products :cite[a31] :cite[n1k] :cite[g8q] :cite[cx6] :cite[ekx]. Regardless of the final shape, the headline for sellers is clear: anticipate constraints on preferential routing, stricter separation between owned services, wider API access and data portability, and increased third-party auditability. This is not just a US story. The European Commission previously issued objections concerning self-preferencing in ad tech and is moving to implement the Digital Markets Act with active non-compliance probes across large platforms :cite[csd] :cite[czg]. Across jurisdictions, watchdogs increasingly target gatekeeper leverage, data tie-ins, and product bundling that tilt auctions. Sellers that prepare for a world of enforced neutrality and verifiable transparency will not only avoid downside. They will set a higher bar that buyers reward.

The Near-Term Shockwaves Sellers Should Expect

Antitrust remedies generally aim at three outcomes: remove unfair advantages, open access, and enable oversight. In ad auctions, that translates into five likely pressure points:

  • Neutral auction design: Greater scrutiny on auction routing and tie-breaking, including how unified auctions treat house demand, related entities, and first-party sell-side tools. Expect stronger expectations for auditable fairness.
  • Interoperability and portability: Expanded or standardized APIs that decouple ad server and exchange choices, with practical paths to multihoming. Watch for contractual and technical unbundling pressures.
  • Supply chain transparency: Heavier reliance on ads.txt 1.1, sellers.json, and the OpenRTB SupplyChain Object to establish provenance and reduce ambiguity in reselling chains :cite[c72] :cite[atv] :cite[h08].
  • Commercial constraints: Tighter guardrails on exclusivity, MFN pricing, and deal constructs that disadvantage rival pipes. Legal reviews will move in lockstep with ops and product decisions.
  • Independent oversight: Greater role for third-party auditors, independent measurement, and data validation services. Logs and interfaces will be scoped for compliance as much as for optimization.

For SSPs and publishers, this creates immediate to medium-term implications across stack choices, data architecture, channel diversification, and sales narratives. The upside: a more level field where quality supply, verified transparency, and outcome proof can win share.

A Seller-Side Playbook for the Post-Lawsuit Era

What follows are eight pillars to guide execution. They are intentionally actionable, spanning design, data, commercial policy, and go-to-market. Use them as a checklist and as a storyboard for stakeholders.

1. Neutral Auction by Design: Prove Fairness, Not Just Claim It

You cannot retrofit trust. Design auctions to be demonstrably neutral and create an evidence trail that is simple to explain.

  • Deterministic, documented routing: Publish internal runbooks for traffic allocation, tie-breakers, floors, and bid shading rules. Make sure product, legal, and compliance teams agree on language and enforcement.
  • Separation of concerns: Avoid implicit preference for any exchange or demand source attributable to corporate structure or rev-share. If you co-own pipes, codify and log neutral treatment.
  • Standardized signals: Prefer OpenRTB 2.6 fields and IAB Tech Lab transparency specs over proprietary flags whenever practical :cite[h08] :cite[ac0].
  • Independent testing: Run periodic third-party fairness tests. Share summaries with strategic partners, particularly premium buyers and holding companies.

Sample SQL to monitor potential preferential routing in log-level data:

-- Detect statistically significant differences in win rates that correlate with a specific exchange
WITH agg AS (
SELECT
auction_id,
exchange,
CASE WHEN is_house_bid = 1 THEN 'house' ELSE 'external' END AS bidder_type,
won,
floor_price,
page_domain,
geo_country,
device_type,
hour
FROM auction_logs
WHERE ts >= DATE_SUB(CURRENT_DATE(), INTERVAL 30 DAY)
)
SELECT
exchange,
bidder_type,
COUNT(*) AS auctions,
AVG(won) AS win_rate,
APPROX_QUANTILES(floor_price, 5)[OFFSET(2)] AS median_floor
FROM agg
GROUP BY 1, 2
HAVING auctions > 10000
ORDER BY win_rate DESC;

Interpretation notes: large deltas in win rates for house vs external across like-for-like contexts may indicate design bias or configuration drift. Investigate tie-breakers and priority rules before concluding intent.

2. Interoperability Readiness: Multihome Without Penalty

Design for choice. Even if your stack is consolidated today, assume tomorrow’s remedies make switching costs a scrutiny hotspot.

  • Header bidding first: Treat client-side and server-side header bidding via Prebid as a primary path to demand diversity and auction competition. Keep your Prebid versions current and modules lean.
  • Ad server abstraction: Avoid hard dependencies on a single ad server’s idiosyncrasies. Normalize line item taxonomies and creative validations so that parallel ad servers remain plausible.
  • API adapters: Build and maintain pluggable adapters for campaign trafficking, reporting, and creative review. Consider open-sourcing non-differentiating adapters to reduce custom work.
  • Data portability contracts: Negotiate mutual data export rights with reasonable SLAs. Anticipate audit needs for migration or concurrent serving periods.

OpenRTB 2.6 bid request snippet with best-practice signals:

{
"id": "req-123",
"tmax": 300,
"source": {
"tid": "trans-abc",
"ext": {
"schain": {
"ver": "1.0",
"complete": 1,
"nodes": [
{"asi": "publisher.com", "sid": "123", "hp": 1, "rid": "req-123", "name": "PubCo"}
]
}
}
},
"site": {"domain": "news.example.com", "page": "https://news.example.com/market"},
"user": {"ext": {"consent": "GPP_STRING"}},
"device": {"ua": "Mozilla/5.0", "ip": "x.x.x.x"},
"imp": [{
"id": "1",
"banner": {"w": 300, "h": 250},
"pmp": {"private_auction": 0},
"bidfloor": 0.5,
"ext": {
"sda": {
"segtax": 600,
"segclass": ["auto_intenders"],
"provider": "publisher.com"
}
}
}]
}

Notes: include schain and SDA-like extensions where appropriate. Validate with the latest IAB Tech Lab specs.

3. Supply Path Transparency: Make Your Inventory Verifiable

Buyers are already tightening supply path optimization. In a post-lawsuit landscape, provenance becomes table stakes.

  • Ads.txt 1.1 hygiene: Adopt the new directives that link to sellers.json files and improve validation. Keep your ads.txt and app-ads.txt current and machine-parseable :cite[c72] :cite[atv] :cite[bzw].
  • Clean sellers.json: Ensure that your sellers.json reflects accurate publisher entries, domains, and relationship types. Keep naming consistent with OpenRTB fields :cite[ac0] :cite[h08].
  • SChain enforcement: Require complete, correct schain nodes from intermediaries. Penalize or downrank paths with missing or conflicting nodes.
  • Transparency reporting: Publish aggregate reports on authorized partners, path changes, and invalid traffic handling to build buyer confidence.

Quick Python utility to validate ads.txt against linked sellers.json references:

import requests
from urllib.parse import urljoin
def fetch_ads_txt(domain):
url = f"https://{domain}/ads.txt"
r = requests.get(url, timeout=10)
r.raise_for_status()
return r.text.splitlines()
def parse_sellers_json(base_url):
url = urljoin(base_url, "sellers.json")
r = requests.get(url, timeout=10)
if r.status_code != 200:
return None
return r.json()
def extract_sellers_links(ads_txt_lines):
links = []
for line in ads_txt_lines:
line = line.strip()
if not line or line.startswith("#"):
continue
parts = [p.strip() for p in line.split(",")]
if len(parts) >= 3:
advertising_system = parts[0]
links.append(f"https://{advertising_system}/sellers.json")
return sorted(set(links))
domain = "news.example.com"
ads = fetch_ads_txt(domain)
sellers_links = extract_sellers_links(ads)
for link in sellers_links:
try:
data = parse_sellers_json(link)
status = "OK" if data else "Not found"
except Exception as e:
status = f"Error: {e}"
print(link, status)

This does not prove legitimacy by itself, but it surfaces missing sellers.json endpoints and routing anomalies quickly.

4. First-Party Data That Respects the Rules: Seller-Defined Audiences, Contextual, and Clean Rooms

Identity that scales must pass both performance and policy tests.

  • Lean into SDA: Use Seller-Defined Audiences to describe first-party cohorts consistently in bid requests. Buyers want privacy-preserving alternatives that still align to business outcomes :cite[iai] :cite[dju].
  • Contextual plus outcomes: Pair contextual signals with outcome data to learn which placements and narratives drive results. Use A/B designs that do not hinge on cross-site identifiers.
  • Clean room pragmatism: For premium deals, adopt interoperable clean room workflows with clear governance for log-level joins. Keep schemas simple and consent signals auditable.
  • Minimize data hoarding: Retain only what you need, for as long as you need it. Regulators reward proportionality, and buyers reward vendors who take privacy by design seriously.

5. Deal Mechanics: From PMPs to Auction Packages Built for Proof

Programmatic guaranteed and private marketplaces are not just revenue. They are control surfaces for transparency and outcome evidence.

  • Auction packages: Standardize themed bundles by content category, attention traits, and supply paths with predictable floors. Expose clear documentation and test plans.
  • Outcome-linked pricing: Where viable, test uplift guarantees or cost-per-outcome constructs with tight measurement protocols and redundancy checks.
  • CTV specifics: For podded video, adopt OpenRTB 2.6 pod bidding conventions and label ad pods clearly for competitive separation. Share pod simulation results with buyers :cite[h08].
  • Brand suitability by default: Ship with recognized suitability taxonomies, provide simple pre-flight tests, and backstop with manual QA for high-value deals.

6. Contracts and Commercial Guardrails That Age Well

What helps today must not hurt you in discovery tomorrow.

  • No sneaky MFNs: Most Favored Nation clauses that freeze innovation or foreclose rivals will not age well in a remedies-heavy market. Keep terms flexible and narrow.
  • Exclusivity with limits: If exclusivity is unavoidable, make it time-bound and scope-limited. Document pro-competitive rationales.
  • Audit and termination rights: Codify reciprocal data access and clear termination paths to mitigate lock-in narratives.
  • Transparency SLAs: Define minimum data detail, freshness, and integrity checks. Align these with your product roadmap to avoid over-promising.

7. Observability and Compliance Tooling: Make Audits Boring

If you can pass an audit without a war room, your pipeline is mature.

  • End-to-end logging: Preserve immutable logs for auctions, demand routing, floor changes, and creative decisions. Keep clear data lineage.
  • Automated consistency checks: Continuously validate ads.txt, sellers.json, schain, and consent signals. Alert on drift.
  • Data contracts: Formalize schemas and SLAs internally. Use contract tests to catch breaking changes before they hit buyers.
  • External attestations: Where practical, adopt industry certifications or publish independent assessments. Buyers retain vendors who reduce internal risk.

A basic data contract example in YAML to validate schain presence:

contract: "supply_integrity_v1"
checks:
- name: "schain_present"
type: "field_presence"
field: "source.ext.schain"
required: true
- name: "ads_txt_alignment"
type: "lookup"
request_field: "seller_id"
reference_source: "sellers_json_registry"
on_fail: "reject_and_alert"

8. Org Readiness: Align Product, Legal, and Sales Around a Compliance Narrative

Treat compliance as a value story, not a tax.

  • Executive alignment: Ensure product, sales, and legal leaders agree on neutral auction principles and messaging. Run tabletop exercises for buyer questions.
  • Frontline enablement: Train sellers to handle RFP questions on transparency, data, and remedies. Provide one-pagers and redline-ready contract templates.
  • Partner scorecards: Rate intermediaries by transparency, data quality, and response SLAs. Use this to rationalize partners and defend choices in audits.
  • Roadmap guardrails: Make a habit of antitrust issue-spotting in design reviews. Document decisions and alternatives considered.

Channel-Specific Notes: Web, App, and CTV

Each surface brings unique constraints that intersect with antitrust themes.

Open Web

  • Header bidding and first-price auctions are mature, but fairness proof still varies widely. Focus on log granularity and standardized reporting.
  • Ads.txt 1.1 plus sellers.json consistency is non-negotiable. Consider publishing a short methodology note on how you manage authorized sellers and resellers :cite[c72] :cite[atv].
  • SDA adoption is accelerating as buyers reduce third-party ID reliance. Keep taxonomies tight and measurable for brand lift and performance.

    Mobile App

  • App-ads.txt remains unevenly implemented across long-tail apps. Maintain monitoring routines and remove unauthorized lines quickly.
  • SDK transparency matters. Document SDK versions, data flows, and compliance with platform policies. Buyers will ask.
  • Work with MMPs and clean rooms for outcome measurement that complies with platform privacy requirements.

    Connected TV

  • Inventory fragmentation and multiple resellers create duplicative paths. Enforce schain, maintain one-hop clarities, and communicate pod-level transparency.
  • Adopt standard signals for channel, content, and ad pod attributes. Buyers want apples-to-apples visibility across FAST and AVOD.
  • Expect stronger scrutiny of exclusivity between OEM OS, app programmers, and sell-side platforms as regulators watch gatekeeper leverage.

    How Red Volcano Can Help

    As a specialized supply-side intelligence platform, Red Volcano focuses on observable data that underwrites trust.

    • Magma Web for discovery and diligence: Identify publishers and apps with clean supply chains, stable ads.txt and sellers.json profiles, and consistent tech stacks.
    • Technology stack tracking: Detect shifts in ad server usage, header bidding modules, and SDK versions that may introduce compliance risk.
    • Ads.txt and sellers.json monitoring: Alert on unauthorized lines, broken links, and conflicting relationships that could erode buyer confidence.
    • Mobile SDK and CTV intelligence: Map partner graphs across app and CTV ecosystems to spot duplicative resells and prioritize direct paths.

    This data backbone helps SSPs rationalize onboarding pipelines, enables publisher teams to de-risk RFPs, and gives intermediaries a defensible transparency narrative in a remedies-first market.

    KPI Framework: What To Measure and Why

    Measurement is the heartbeat of credibility. Consider a balanced scorecard that covers integrity, performance, and adoption.

    • Transparency integrity: percent of inventory with valid schain, ads.txt freshness rate, sellers.json alignment score.
    • Performance signal quality: win rate variance across exchanges for like-for-like inventory, bid landscape stability, error rates in consent signals.
    • Buyer adoption: average deal cycle length, share of spend through verified direct paths, number of buyers activating SDA cohorts.
    • Compliance readiness: time to furnish audit logs, number of open compliance issues, remediation SLA adherence.

    Pricing and Packaging Implications

    Sellers with stronger compliance posture and observable supply chains can command premium packaging.

    • Trust tiers: Offer premium tiers that guarantee specific transparency SLAs and audit support. Price the peace of mind.
    • Data add-ons: Package SDA taxonomies, attention signals, and contextual enrichments as add-ons with usage-based pricing.
    • Verification credits: Include independent verification or Red Volcano intelligence credits in higher-tier deals to lower buyer evaluation costs.

    Scenario Planning: Three Futures To Prepare For

    Anticipating remedies helps you choose robust strategies.

    • Structural separation: If ad server and exchange are split, expect short-term disruption followed by more competitive paths. Prioritize adapter parity and migration runbooks. Reference: DOJ seeking breakup proposals :cite[cx6].
    • Conduct remedies: If neutrality and access rules tighten without a breakup, auditability will be the main arena. Invest in observability and third-party attestations.
    • No major change: Even in a status quo-ish outcome, buyer behavior has shifted. SPO will favor clean, direct, and well-documented paths. Sellers who upgraded transparency still win.

    Common Pitfalls To Avoid

    • Paper compliance: Documenting neutrality without observable logs and tests will not pass skeptical buyers or regulators.
    • One-off custom work: Avoid bespoke adapters that are fragile. Standardize and abstract to keep maintenance manageable.
    • Over-collecting data: Retaining more than you need increases exposure without performance upside. Practice data minimization.
    • Ignoring long-tail issues: Most brand damage comes from the tail. Maintain hygiene across all supply, not just premium domains and channels.

    A Short Buyer Script Your Team Should Rehearse

    Equip your sales and account teams with crisp, credible messaging.

    • Our auctions: Neutral by design, documented, and periodically tested by third parties. We can share summaries and methodology.
    • Our supply chain: Ads.txt 1.1, sellers.json, and schain consistency enforced. We publish path-level integrity metrics and remove failing paths.
    • Our data: First-party audience cohorts via SDA with clear provenance. Privacy by design and clean room options for premium deals.
    • Our readiness: APIs and adapters for multihoming. If your team wants to test alternate ad servers or exchanges, we can support side-by-side experiments.

    Practical Next Steps: A 90-Day Plan

  • Days 0 to 30: audit and hygiene
    • Audit: Complete a supply integrity audit across ads.txt, sellers.json, schain, and consent signals. Prioritize top 20 domains and apps.
    • Fix: Close critical gaps. Remove unauthorized resellers. Update outdated records. Establish weekly monitoring.
    • Document: Write a two-page neutrality and transparency overview. Align product, legal, and sales.
  • Days 31 to 60: productize trust
    • Build: Add automated checks in CI for transparency specs and consent signals. Ship internal dashboards.
    • Package: Create two trust tiers with SLAs and verification options. Update pricing sheets.
    • Pilot: Run fairness and SPO pilots with two strategic buyers. Share log-backed results.
  • Days 61 to 90: scale and message
    • Certify: Pursue relevant attestations or third-party assessments. Publish a short transparency report.
    • Enable: Train sales on the new script and objection handling. Provide one-pagers and codeable RFP responses.
    • Market: Announce your trust posture and pilots. Use Red Volcano insights in content and sales collateral.

    Conclusion: Build for Scrutiny, Sell on Proof

    Antitrust enforcement is reshaping how ad auctions must work. The sellers who thrive will not wait for remedies to be forced upon them. They will adopt neutral-by-design principles, make supply path integrity observable, package data in privacy-forward ways, and turn compliance into a commercial advantage. This is not just defensive posture. It is a growth strategy. Buyers are shifting budgets toward partners that remove risk and provide evidence, not just promises. Use this moment to standardize your stack around interoperability and transparency, build credible proofs, and tell a trust story that wins in the post-lawsuit era. Red Volcano will keep investing in SSP and publisher intelligence that makes this easier. If you want to test where you stand, start with a simple question: can you prove to a skeptical buyer that your auctions and supply paths are fair and verifiable today? If the answer is yes, the rest gets a lot easier.

    References

  • NPR: Should a court break up Google? Closing arguments on remedies. https://www.npr.org/2025/05/30/nx-s1-5413538/google-search-antitrust-remedies-trial-closing-arguments. Accessed 2025-08-11. :cite[ekx]
  • New York Times: Read the Antitrust Ruling Against Google. https://www.nytimes.com/interactive/2025/04/17/technology/google-ads-antitrust-ruling.html. Accessed 2025-08-11. :cite[a31]
  • Simpson Thacher summary: District Court Rules Google Is a Monopolist in Ad Tech. https://www.stblaw.com/about-us/publications/view/2025/04/25/district-court-rules-google-is-a-monopolist-in-ad-tech. Accessed 2025-08-11. :cite[n1k]
  • Deadline: Google Violated Antitrust Law by Maintaining Digital Ad Monopoly. https://deadline.com/2025/04/google-antitrust-monopoly-advertising-1236370826/. Accessed 2025-08-11. :cite[g8q]
  • Reuters: U.S. seeks breakup of Google’s ad-tech products after judge finds illegal monopoly. https://www.reuters.com/sustainability/boards-policy-regulation/us-seeks-breakup-googles-ad-tech-products-after-judge-finds-illegal-monopoly-2025-05-06/. Accessed 2025-08-11. :cite[cx6]
  • European Commission Competition Policy Report 2023: Concerns on self-preferencing in ad tech. https://www.eumonitor.eu/9353000/1/j4nvhdfcs8bljza_j9vvik7m1c3gyxp/vmbbgkox45zn. Accessed 2025-08-11. :cite[csd]
  • Lexology overview: DMA non-compliance investigations into Alphabet. https://www.lexology.com/gtdt/tool/workareas/report/competition-in-digital-markets/chapter/european-union. Accessed 2025-08-11. :cite[czg]
  • IAB Tech Lab: Upgrade to Ads.txt 1.1 with Supply Chain Transparency + new APIs. https://iabtechlab.com/upgrade-to-ads-txt-1-1-with-iab-tech-lab-supply-chain-transparency-introducing-new-apis/. Accessed 2025-08-11. :cite[c72]
  • IAB Tech Lab: ads.txt Version 1.1. https://iabtechlab.com/wp-content/uploads/2022/04/Ads.txt-1.1.pdf. Accessed 2025-08-11. :cite[atv]
  • IAB Tech Lab: OpenRTB 2.6. https://iabtechlab.com/wp-content/uploads/2022/04/OpenRTB-2-6_FINAL.pdf. Accessed 2025-08-11. :cite[h08]
  • IAB Tech Lab: Security and Fraud specs overview including sellers.json and SupplyChain. https://iabtechlab.com/security-fraud/. Accessed 2025-08-11. :cite[ac0]
  • IAB Tech Lab roadmap notes including Seller-Defined Audiences. https://iabtechlab.com/is-this-on-your-2023-roadmap/. Accessed 2025-08-11. :cite[iai]