Polymarket Accuses Kalshi of Spying in Escalating Rivalry

The Polymarket and Kalshi rivalry has always been competitive, but now it has turned hostile. Polymarket has opened a formal internal investigation into its closest competitor. The prediction market giant is accusing Kalshi of systematically copying its products, campaigns, and launches. CEO Shayne Coplan and his team have compiled what they call a “copycat” dossier, and the allegations inside it go well beyond ordinary competitive imitation. Polymarket suspects corporate espionage, and possibly moles within its own company.

A Rivalry That Has Turned Personal

Both Polymarket and Kalshi operate prediction markets, platforms where users can place real-money wagers on the outcomes of real-world events. Sports results, election outcomes, economic data releases, and even weather events all serve as the basis for contracts. Both platforms have attracted enormous Silicon Valley backing. Polymarket has raised around $2 billion and is targeting a $15 billion valuation. Kalshi has raised approximately $2.6 billion and currently carries a valuation of $22 billion.

The Polymarket versus Kalshi rivalry has deepened as both have pushed aggressively into the US market. Polymarket originally launched in the US in 2020 before exiting in 2022 under regulatory pressure. Kalshi, founded in 2018, stepped into that gap and built a strong foothold in political and event-based markets. Since Polymarket’s return, the two have competed head-to-head for users, investors, and market share.

That competition is apparently now crossing lines. Polymarket’s head of marketing, Matthew Modabber, told reporters the situation had gone too far. He said there had been far too many coincidences, accused Kalshi of deliberate bad-faith copying. He also described the pressure as relentless.

Windows Tinted, Dossier Compiled

The most striking detail in the investigation concerns office surveillance. Paradigm, a venture-capital firm that backs Kalshi, leases offices directly across the street from Polymarket’s Soho headquarters in New York City. Employees at Polymarket began to worry that staff or associates in those offices could observe parts of their operations. In response, the company tinted its office windows earlier this year to limit what could be seen from the street.

Paradigm dismissed the concern publicly, calling it laughable. But Polymarket’s team had already moved on to the bigger picture: a documented record of alleged copying that stretches back more than a year.

Two Incidents That Deepened Suspicions

The dossier draws on a pattern of events, but two in particular pushed Polymarket to escalate its concerns.

The first came in February in Manhattan. Polymarket had planned a pop-up grocery store event for around 300 customers. Leases and production arrangements had been finalised months in advance. Nine days before the launch, Kalshi ran its own grocery promotion at a separate New York market, offering vouchers and promoting wagers tied to the price of eggs. A source at Polymarket said the timing was deliberate, designed to dilute the impact of an event that carried personal significance for Coplan, who grew up in New York.

Kalshi’s communications team said the timing was coincidental and the campaign had been in development long before Polymarket’s event was announced.

The second incident came in April. Polymarket was preparing to launch perpetual futures contracts, known as perps, which allow users to speculate on asset prices without actually owning them. An hour before Polymarket’s official announcement, a trade publication reported Kalshi’s own plans for a near-identical product. Insiders at Polymarket found the timing too precise to be coincidental.

Kalshi responded that its perps launch had been in development since 2024 and that the date had already been visible in a social media teaser posted earlier that month.

A Paper Trail of Alleged Copying

The Polymarket and Kalshi rivalry has produced its own paper trail. The dossier Polymarket compiled includes screenshots of social media posts, app interfaces, and product announcements. One example involves a Polymarket football betting ad from August 2024, which targeted California users with specific visuals and copy. Kalshi allegedly followed with a near-identical version shortly after.

Kalshi denied copying, arguing that the phrases and formats in question are widely used across the industry and do not constitute infringement. Kalshi spokesperson Jack Such was direct in his response, calling the investigation sad and borderline delusional, and saying Kalshi would keep building while Polymarket chased shadows.

What This Says About Prediction Markets

The Polymarket Kalshi rivalry plays out against a backdrop of intense regulatory scrutiny and enormous financial stakes. Both platforms are fighting legal battles across multiple US states while simultaneously racing to launch new products, attract users, and secure market position. In that environment, competitive intelligence matters enormously, and the line between monitoring a rival and crossing into misconduct can be thin.

Polymarket has stopped short of filing any legal action so far. But the window tinting, the compiled dossier, and the public statements from its marketing team all point to a company that believes it is dealing with something more than ordinary competition. Whether that belief holds up under scrutiny: we will see.