Amazon built a $68.6 billion advertising business on a simple premise: shoppers browse, and while they browse, they see ads. That premise is now on trial.

Perplexity AI filed a 96-page opening appeal brief with the United States Court of Appeals for the Ninth Circuit on April 1, 2026, arguing that a preliminary injunction won by Amazon in March fundamentally misapplies federal computer fraud law. The case, numbered 26-1444, asks whether a 1984 statute designed to punish computer hackers can be repurposed to block AI shopping assistants that users voluntarily install on their own computers. If the Ninth Circuit sides with Perplexity, the ruling would strip Amazon of one of its most powerful legal tools for keeping third-party AI agents away from its marketplace - and, critically, away from its advertising inventory.

The financial stakes are not abstract. Amazon's advertising revenue reached $21.3 billion in the fourth quarter of 2025 alone, growing 23 percent year-over-year. For the full year, the segment generated $68.6 billion. CFO Brian Olsavsky noted during the Q4 earnings call that advertising contributed more than $12 billion of incremental revenue to Amazon during 2025. That money flows primarily from Sponsored Products and Sponsored Brands - the ads shoppers see when they search for goods on Amazon's platform. Remove the shoppers' eyeballs, and the model breaks.

What the lawsuit is actually about

The dispute centers on Perplexity's Comet browser, a Chromium-based application that includes an optional AI assistant capable of browsing websites, finding products, and completing purchases on behalf of users. Perplexity launched Comet on July 9, 2025, initially restricting access to subscribers of its $200-per-month Max plan. The browser was made broadly available on October 2, 2025, after millions joined a waitlist.

The Comet Assistant sits inside the browser itself. Users activate it by clicking a tab in the upper right corner of the display. Once on, the assistant can navigate Amazon at the user's direction - searching for products, comparing options, and facilitating purchases. According to the appeal brief, the assistant works by taking screenshots or HTML snapshots of the browsing session, sending encrypted versions to Perplexity's servers for processing, and then receiving instructions back. The screenshots are deleted within 30 days. Perplexity's servers never connect directly to Amazon's computers.

That architectural detail matters enormously. Amazon's own expert conceded in the district court that there are "no direct requests from Perplexity hosts to Amazon.com" and that data travels from Amazon to the user's browser first, then to Perplexity. The assistant cannot log into a user's Amazon account independently. For purchases, it requires additional manual authorization from the user.

Why does Amazon care? Because when an AI assistant shops on behalf of a user, it skips the ads. It bypasses sponsored product listings, recommendations, and other advertising placements that constitute the bulk of Amazon's advertising revenue. The brief alleges that Amazon's true motivation is to identify and block the Comet Assistant so it can force "customers to view its advertisements" - a characterization drawn from Amazon's own internal complaints that advertisers do not pay for their ads to be shown to automated agents.

The $69 billion question

Amazon's advertising business has grown at an extraordinary pace. In Q1 2025, revenue reached $13.9 billion, a 19 percent increase. By Q2, it climbed to $15.7 billion, up 22 percent. Q3 delivered $17.7 billion, also growing 22 percent year-over-year. And the fourth quarter posted the strongest performance of all, reaching $21.3 billion at 23 percent growth.

The acceleration is striking. Amazon is now the third-largest digital advertising platform globally, behind only Meta and Alphabet. The Trade Desk CEO Jeff Green noted during a November 7, 2025, earnings call that Amazon would likely generate approximately $70 billion in advertising for the year, with roughly 90 percent in Sponsored Listings competing directly with Google Search and emerging AI search platforms.

That 90 percent figure illuminates the vulnerability. If the vast majority of Amazon's ad revenue comes from search-based sponsored listings - the kind that appear when a human user types a query into Amazon's search bar - then any technology that replaces human browsing with AI-assisted shopping directly threatens the business model. An AI assistant does not browse. It does not scroll past sponsored products. It does not get distracted by Amazon's recommendation algorithms. It finds what the user asked for and facilitates the purchase. In that transaction, advertising ceases to have a function.

This is not a hypothetical concern. Amazon moved its AI-powered shopping prompts out of open beta on March 25, 2026, transitioning them to general availability in the United States and introducing CPC charges for AI-generated shopping conversations. The decision to monetize these prompts came after a free beta period that began in November 2025. Amazon clearly sees AI-mediated shopping as a growth opportunity - but only when it controls the AI doing the mediating.

Amazon's own AI agent contradictions

The appeal brief raises a pointed observation about Amazon's conduct. While suing Perplexity for deploying an AI shopping agent, Amazon simultaneously operates its own. Amazon's Rufus AI shopping assistant reached more than 300 million users throughout 2025 and generated nearly $12 billion in incremental annualized sales. Rufus can track prices, monitor deals, and even complete purchases autonomously through an auto-buy feature. Users who engage with Rufus complete 60 percent more purchases during shopping sessions, according to Amazon's own metrics.

More telling is Amazon's "Buy for Me" feature. Products available through Buy for Me grew from 65,000 at launch to over half a million, enabling Amazon's AI to purchase items from third-party retailer websites - often without those retailers' knowledge or permission. According to the appeal brief, Amazon even listed Perplexity's own merchandise through Buy for Me without Perplexity's consent.

The brief frames this as an unclean hands argument: Amazon cannot invoke equity while engaging in equivalent or worse conduct against third parties. Amazon blocks competitors' AI agents from its marketplace while deploying its own AI agent onto competitors' websites. The asymmetry is difficult to reconcile.

The hacking law question

The legal foundation of Amazon's case rests on the Computer Fraud and Abuse Act (CFAA), a statute Congress enacted in 1984 under the Counterfeit Access Device and Computer Fraud and Abuse Act. At the time, the law targeted people who hacked into computers containing national security information or financial data. Congress subsequently expanded the statute to cover any "protected computer" used in interstate commerce - which, in the internet age, encompasses essentially every computer connected to the web.

Amazon claims Perplexity violated the CFAA by accessing its computer systems without authorization. The claim requires Amazon to establish five independent elements: that Perplexity intentionally accessed a computer, without authorization or by exceeding authorized access, thereby obtaining information from a protected computer, with loss aggregating at least $5,000 in a one-year period.

The appeal brief argues Amazon cannot satisfy any of the five elements, let alone all of them.

On intentional access, Perplexity draws a sharp comparison. A Comet user accessing Amazon from her own computer, the brief states, "is no more equivalent to Perplexity accessing Amazon than a Safari user accessing Amazon from her own computer is equivalent to Apple accessing Amazon." Since Amazon sued only Perplexity and not the users, the company cannot establish that Perplexity itself accessed Amazon's systems.

On authorization, the argument is that Amazon account holders authorized the Assistant to access their own information for their own shopping. No private information beyond what the user can see in the browser window was transmitted. The assistant is, according to the brief, functionally "akin to what a person would see from looking over the user's shoulder."

On the question of obtaining information from a protected computer, the brief is direct: Perplexity never connects to Amazon's servers. Data reaches Perplexity only after passing through the user's browser, a chain Amazon's own expert confirmed.

On financial loss, the brief cites the Supreme Court's 2021 decision in Van Buren v. United States and the Ninth Circuit's 2022 ruling in hiQ Labs, Inc. v. LinkedIn Corp., both of which held that CFAA "loss" requires technological harms such as file corruption. Amazon's real complaint is lost advertising impressions - monetized attention, not the kind of technological injury the statute was designed to address.

What the district court said - and what it did not

United States District Judge Maxine M. Chesney issued the preliminary injunction on March 9, 2026, just one business day after a hearing. But her statements during the hearing revealed ambivalence. Judge Chesney acknowledged that the conduct at issue "almost as if what [Perplexity is] doing shouldn't be covered" by the CFAA. She added that "people ought to be allowed to bring these kinds of shopping assistants in and have them talk." She described herself as "kind of stuck" with a statute that "is SO broad and covers people who may be performing a beneficial act."

Despite these reservations, Judge Chesney granted the injunction, barring Perplexity from accessing Amazon's protected systems using AI agents deployed through the Comet browser. She denied Perplexity's request for a $1 billion bond. The Ninth Circuit subsequently stayed the injunction pending appeal and ordered expedited briefing.

The brief argues that Judge Chesney improperly collapsed the four independent requirements for injunctive relief - likelihood of success on the merits, irreparable harm, balance of equities, and public interest - into a single finding. The court effectively found irreparable harm simply by finding Amazon was likely to succeed on the merits, rather than analyzing each element separately. Amazon produced no evidence that any customer had complained about or encountered problems with the Comet Assistant.

Why the ad tech industry is watching

The implications extend far beyond two companies fighting over a browser. The case sits at the center of a much larger question: who controls what happens when an AI agent visits a commercial website?

The question has become urgent. Amazon, Google, and IAB Tech Lab simultaneously accelerated autonomous campaign tools in November 2025, marking a dramatic infrastructure buildout around agentic advertising. Walmart Connect announced its own agentic advertising strategy on January 6, 2026, positioning its retail media network to compete with autonomous shopping systems. Google launched the Universal Commerce Protocol on January 11, 2026, establishing open-source technical standards for AI agents to execute purchases across different retail platforms.

The contrast with Amazon's approach is stark. While Google builds open protocols for AI-mediated commerce and Walmart explicitly welcomes third-party AI agents, Amazon uses legal action to block them. Amazon executive Daniel Danker stated at Walmart that the retailer would "not block things on a speculative or hypothetical concern," a direct rebuke of Amazon's posture. Walmart's global advertising business grew 46 percent to nearly $6.4 billion in fiscal year 2026, with Walmart Connect up 41 percent in Q4 - growth fueled in part by embracing agentic commerce rather than fighting it.

If the Ninth Circuit upholds the injunction, platform operators would gain confirmation that the CFAA can be used to restrict third-party AI agents their own users choose to employ - even when those agents access only the user's account data, with the user's permission, for the user's benefit. That precedent would give every major e-commerce platform a legal veto over client-side AI software, regardless of consumer preference.

If the court reverses, the ruling would establish that a statute written in the era of mainframe computers and dial-up modems does not reach AI agents operating locally on a user's device at the user's instruction. Platform operators would almost certainly respond with technical countermeasures and updated terms of service, but the legal threat would diminish considerably.

The Amazon case is not Perplexity's only legal challenge. Reddit filed a separate federal lawsuit against Perplexity on October 22, 2025, alleging the AI company circumvented anti-scraping controls to access platform data. That case involves different conduct - web scraping via search engine results pages rather than AI-assisted shopping through a locally installed browser - but it adds to the legal pressure Perplexity faces.

Amazon has also been hardening its governance posture across the board. The company updated its Business Solutions Agreement effective March 4, 2026, introducing a formal Agent Policy requiring AI agents to identify themselves as automated systems and comply with new access rules. The policy gives Amazon contractual authority to revoke access from any automated software that fails to meet its transparency requirements - a framework far broader than any single lawsuit.

Amazon is also changing how it collects advertising revenue from sellers, announcing that ad costs will auto-deduct from seller proceeds starting April 15, 2026. At the scale of $68.6 billion in annual advertising revenue, even small changes to billing mechanics carry significant financial implications. The shift underscores how central advertising has become to Amazon's overall profitability and how aggressively the company protects that revenue stream.

The user-agent string controversy

One technical detail deserves closer examination. Amazon alleged that Perplexity configured Comet to transmit the same user-agent string used by Google Chrome, making the AI assistant indistinguishable from a human browsing session. The user-agent string is a piece of text that browsers send to websites to identify themselves. Amazon argued this lack of transparency violated industry standards.

The appeal brief counters that Comet uses substantially the same user-agent string as other Chromium-based browsers, including Microsoft Edge, Brave, and Opera. None of those browsers use unique identifiers either. The brief argues Perplexity has no legal duty to equip Comet with any particular user-agent string, and that Amazon's real reason for demanding the change was so it could identify and block Comet traffic - not for any legitimate security purpose, but to protect its advertising business.

The debate reveals a tension at the heart of the modern internet. Websites have grown accustomed to identifying and categorizing their visitors. Advertising systems depend on distinguishing human traffic from automated traffic. When an AI agent looks indistinguishable from a human browser, the entire infrastructure of impression measurement, click tracking, and conversion attribution breaks down. Amazon's advertising customers pay for human impressions. If a growing share of traffic comes from AI agents that skip ads entirely, the value proposition of Amazon's advertising platform erodes.

What comes next

The Ninth Circuit heard the case on an expedited schedule. When the decision arrives, it will establish one of the first major legal precedents governing AI agents' access to commercial websites. The outcome matters not just for Amazon and Perplexity but for every company building AI assistants, browsers, or autonomous shopping tools.

The advertising industry generates hundreds of billions of dollars annually on the assumption that humans see ads while interacting with digital platforms. AI agents that shop, browse, and transact on behalf of humans challenge that assumption at its core. Whether platforms can legally prevent those agents from operating - or whether users have the right to deploy whatever software they choose on their own devices - is a question that will shape the next decade of digital commerce.

Amazon has built a business that depends on attention. Perplexity has built a product designed to make attention unnecessary. Something has to give.

Timeline

Summary

Who: Perplexity AI, represented by Quinn Emanuel Urquhart & Sullivan, LLP, is challenging Amazon.com Services, LLC before the United States Court of Appeals for the Ninth Circuit. The case involves the first federal lawsuit Amazon has filed against an AI company over autonomous shopping agents.

What: Perplexity filed a 96-page opening appeal brief on April 1, 2026, arguing that the Computer Fraud and Abuse Act does not apply to an AI assistant that runs locally on a user's device, accesses only the user's own account data, and never connects directly to Amazon's servers. The brief challenges a preliminary injunction issued on March 9, 2026, that barred Comet's AI Assistant from accessing Amazon's password-protected accounts.

When: The underlying lawsuit was filed on November 4, 2025. The preliminary injunction was issued on March 9, 2026. The opening appeal brief was filed on April 1, 2026. The Ninth Circuit is hearing the case on an expedited schedule.

Where: The original case was filed in the United States District Court for the Northern District of California, Case No. 25-cv-09514, before Judge Maxine M. Chesney. The appeal is pending in the Ninth Circuit, Case No. 26-1444.

Why: At its core, the dispute is about advertising revenue. Amazon's $68.6 billion advertising business depends on human shoppers seeing sponsored listings, display ads, and recommendations while browsing its marketplace. AI shopping assistants that bypass those advertising elements threaten the economic foundation of the platform. Amazon argues Perplexity violated federal hacking law. Perplexity argues Amazon is weaponizing a 1984 criminal statute to protect advertising margins from competitive technology that users voluntarily choose to install.

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