Consumers celebrated a historic legal win in an antitrust class-action lawsuit against Amazon.com when U.S. District Judge John H. Chun granted class certification to the largest class in US history, encompassing about 288 million Americans, according to attorneys at Hagens Berman.

The certified class includes all US consumers who on or after May 26, 2017, purchased five or more new physical goods from third-party sellers on Amazon. Per the order certifying the class, “Plaintiffs' economics expert, Dr. Pathak, Ph.D., using transactional data provided by Amazon, estimates that around 34 billion third-party transactions and around 300 million consumers across the United States have been ‘affected by Amazon's conduct.’”

“When Amazon sought to fight this class certification, its argument amounted to ‘we’re too big to fail,’ and we hope this consumer win sends a wake-up call that the world’s largest retailer is not above the law,” said Steve Berman, managing partner and co-founder of Hagens Berman which serves as court-appointed interim co-lead counsel in the lawsuit. “This is a victory for millions of US consumers and a historic day for consumer-protection law and class actions.”

The independently researched antitrust lawsuit De Coster et al v. Amazon.com Inc. was originally filed in 2021 and accuses Amazon of forcing its customers to pay artificially increased prices for products purchased via its platform, violating federal price-fixing laws.

Judge Chun’s granting of class certification followed the certification hearing on Aug. 1, 2025, and an order first filed under seal on Aug. 7, 2025. In class-action law, class certification is a major case milestone, signaling the court’s acknowledgement that the case passes many definitive prerequisites and is allowed to continue as a class case.

The case stands among 12 total active cases filed by Hagens Berman against the world’s largest retailer, ranging from price-fixing concerning e-books, Apple products and Audible audiobooks to price-gouging of essential goods during the onset of the COVID-19 pandemic.

“Our firm is proudly litigating a dozen active cases against Amazon, and in De Coster, our antitrust team revealed that the retailer was forcing its own customers to pay artificially increased prices for products purchased via Amazon,” Berman said. “We look forward to continuing this case and others seeking to hold Amazon accountable for what we believe to be blatant violations of federal price-fixing laws.”

Boxed In

The 50-page order was originally filed on Aug. 6, 2025, and unsealed Sept. 2, 2025, and states, “As reflected below, the core of this class certification dispute concerns commonality and predominance. Being fully advised, upon engaging in the rigorous analysis Rule 23 requires, the Court finds that Plaintiffs have met their burden, by a preponderance of the evidence, regarding commonality, predominance, and the rule's other requirements. For these reasons, which are explained in detail below, the Court GRANTS the motion.”

The order details plaintiffs’ allegations including Amazon’s contractual, anti-discounting (“parity”) policy through which Amazon denies customers the "benefits of lower prices and fees" as well as Amazon’s Select Competitor Featured Offer Disqualification (SC-FOD) algorithm, which plaintiffs say Amazon uses as its primary "tool for securing third-party sellers' price parity” by “disqualify[ing] a seller’s offer from winning the ‘Buy Box’” where most sales are made, if the seller’s offer does not comply with the parity requirement. The order further details Amazon’s internal documents that suggest Amazon’s awareness of its harmful impact on third-party sellers and that the company’s policies harmed consumers. Price parity or most favored nations clauses, sometimes referred to as Platform Most Favored Nations clauses (“PMFNs”), are a frequent subject of regulatory action.

Judge John H. Chun ruled, “After reviewing the evidence, the Court concludes that Plaintiffs have presented common proof, by a preponderance of the evidence, that Amazon has implemented certain policies and practices concerning third-party sellers that function as a PMFN policy.”

Delivering Consumer Wins

Since the lawsuit’s filing, multiple attorneys general have benefitted from the firm’s economic expertise and research: in 2021 Washington, D.C. attorney general, Karl Racine, filed a similar case against Amazon, repeating claims brought by Hagens Berman in 2020, and in 2022, California AG, Rob Bonta, filed a similar case against Amazon, repeating claims brought by Hagens Berman in its most recent antitrust cases against the retailer. The FTC also raised similar claims when it filed its enforcement action against Amazon in 2023.

In 2021, the court appointed the firm to a leadership position in the case, and Judge Chun’s class certification order affirms the firm’s position as co-lead counsel for the class. Previously, U.S. District Court Judge Ricardo S. Martinez allowed the antitrust lawsuit against Amazon.com to proceed in a 2023 order, denying the online retail giant’s motion to dismiss monopoly claims and claims that its anticompetitive price agreements with third-party sellers caused consumers to pay supracompetitive prices. Judge Martinez also sided with plaintiffs in 2023 when it ordered Amazon to produce sales data that it sought to protect. In 2024, Judge Chun denied Amazon’s renewed motions to dismiss the De Coster et al. v. Amazon.com Inc. and Frame-Wilson et al. v. Amazon.com Inc. lawsuits after the plaintiffs amended their complaints. Preceding his order on class certification, Judge Chun denied Amazon’s motion to exclude plaintiffs’ expert.

Read more about the firm’s lawsuit against Amazon on behalf of US consumers.

About Hagens Berman

Hagens Berman is a global plaintiffs’ rights complex litigation law firm with a tenacious drive for achieving real results for those harmed by corporate negligence and fraud. Since its founding in 1993, the firm’s determination has earned it numerous national accolades, awards and titles of “Most Feared Plaintiff’s Firm,” MVPs and Trailblazers of class-action law. More about the law firm and its successes can be found at hbsslaw.com. Follow the firm for updates and news at @ClassActionLaw.

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When Amazon sought to fight this class certification, its argument amounted to ‘we’re too big to fail,’ and we hope this consumer win sends a wake-up call that the world’s largest retailer is not above the law.