The complaint, City of Dearborn Heights Act 345 Police & Fire Retirement System v. Duolingo, Inc., claims that the company knowingly introduced user friction through increased ad volume and subscription upsells, despite internal A/B testing that warned these tactics would degrade product quality and suppress daily active user (DAU) growth. Plaintiffs argue that leadership failed to disclose these negative trends, which ultimately damaged the company’s financial performance.

Duolingo’s stock faced significant volatility as these issues surfaced. Following a third-quarter earnings report on November 5, 2025, that revealed a slowdown in DAU growth, the share price dropped 25%. Further declines occurred in January 2026 after the CFO resigned and, finally, in February 2026, when the company confirmed 2026 DAU growth projections would be limited to 20%. Investors seeking to serve as lead plaintiff have until December 7, 2026, to file their applications with the court.