A California federal judge dealt a significant blow to a proposed cookie-tracking class action against ad-tech company Magnite, ruling that the plaintiffs could not turn alleged privacy violations into a single, manageable class case. For defense counsel, Lewis v. Magnite offers a practical roadmap for defeating certification in CIPA, wiretap, and online-tracking cases—even where the claims survive the pleading stage.
The court denied certification on multiple independent grounds: individualized consent, class-member identification, Article III injury, damages, typicality, predominance, and superiority. Plaintiffs alleged that Magnite’s “khaos ID” cookie secretly tracked browsing activity for targeted advertising, in violation of CIPA, the federal Wiretap Act, and related privacy theories.
WHY DEFENDANTS CARE
Consent can defeat the class. Because users encountered Magnite technology through different websites, each with different privacy policies, cookie banners, and disclosures, the court concluded that determining notice and consent would require person-by-person analysis—overwhelming any common issue.
Pseudonymous data creates a certification problem. Magnite did not necessarily know the real-world identity behind a tracking ID, and a user could have multiple IDs across browsers or devices while multiple users could share a device. That made it difficult for plaintiffs to establish a reliable, administratively feasible way to identify who belonged in the class.
Standing is now a class-certification weapon. Applying the Ninth Circuit’s Popa v. Microsoft framework, the court held that plaintiffs needed class wide proof of a concrete privacy injury comparable to a traditionally recognized privacy tort—not merely an alleged statutory violation or collection of generic browsing data. The need to determine what information was actually collected and whether it was sufficiently sensitive injected individual issues into Article III standing and Rule 23 predominance.
Damages still need a common method. Plaintiffs also lacked a workable class wide damages model, a separate Rule 23 problem under Comcast.
DEFENSE PLAYBOOK
For defense counsel, Lewis v. Magnite supports an early, evidence-driven certification strategy:
• Build a record showing variation in website disclosures, consent interfaces, and user journeys across publishers or platforms.
• Demonstrate that identifiers are pseudonymous, non-personal, duplicative, shared, or otherwise inadequate to identify class members reliably.
• Develop discovery on the actual categories and sensitivity of data collected, rather than accepting plaintiffs’ generalized “tracking” narrative.
• Force plaintiffs to present a class wide injury theory under Popa, not just a statutory-violation theory.
• Attack the damages methodology before class certification, particularly where the proposed class spans different websites, devices, disclosure regimes, or data types.
TAKEAWAY
The takeaway is simple: a cookie or pixel is not automatically a class action. Plaintiffs still must prove with common evidence who was affected, what they saw and consented to, what data was captured, whether it caused concrete harm, and how damages could be measured across the entire proposed class.
