The lawsuit, filed in the U.S. District Court for the Southern District of New York by plaintiffs Adrian Vazquez, Alexander Foley and Nicholas Ross, claims Kalshi allowed outside companies to intercept users’ communications and platform activity without their knowledge or consent. The plaintiffs seek to represent all individuals who used Kalshi’s digital platforms and whose communications, personally identifiable information, or online activity was allegedly intercepted or disclosed to third parties.

According to the complaint, Kalshi operates an online marketplace where users trade binary event contracts tied to real-world outcomes. The filing says those contracts can involve subjects ranging from entertainment to politics and international affairs, and argues that a user’s activity on the platform can reveal “the events the user considered important, the outcomes the user predicted, the amount of money the user was willing to risk, the user’s confidence in particular outcomes, and the user’s financial gains or losses.”

The plaintiffs contend that users provide extensive personal and financial information to create and fund accounts, including identity verification information, and reasonably expect that information and their trading activity to remain private. The complaint argues that because Kalshi involves wagering-like activity, users have “a heightened privacy interest in keeping their Kalshi activity confidential.”

The complaint alleges Kalshi embedded third-party scripts, pixels and tracking technologies throughout its digital platforms, allowing companies including Google, TikTok, LinkedIn and others to monitor users as they browsed markets, viewed event contracts and placed trades.

“Through these tracking technologies, third parties such as Google, TikTok, LinkedIn, and others were able to monitor users as they interacted with Kalshi’s Digital Platforms,” the complaint states. “This monitoring included, upon information and belief, users’ browsing activity, pages viewed, event contracts reviewed, account interactions, and trades or attempted trades.”

The lawsuit further alleges that Kalshi “employs over 60 different third-party trackers on its website,” including technologies associated with Google, Meta, HypeLab and...