Stack Overflow

Stack Overflow is a question-and-answer website for programmers, launched on September 15, 2008 by Jeff Atwood and Joel Spolsky as a more open alternative to Experts-Exchange. It is the flagship of the broader Stack Exchange Network, which now spans dozens of topical sites. Stack Overflow was acquired by Prosus, a Dutch consumer-internet conglomerate, on June 2, 2021 for approximately US$1.8 billion. The platform pioneered a gamified reputation system in which users earn points for asking good questions and providing helpful answers, with reputation thresholds unlocking editing, voting, and moderation privileges. This design explicitly attempted to address the free-rider problem in volunteer knowledge platforms by providing low-cost, high-frequency status rewards for contribution. At its 2017 peak Stack Overflow processed over 300,000 new questions per month and surpassed 10 million registered accounts. Participation has since declined. Research analysing the contributor pipeline ('From Asking to Answering,' 2020) found that only roughly half of active users who joined after 2014 posted any answer within two years of registering, and the share of accounts that never answer has grown over time. Question volume plateaued around 2.1 million annually between 2016 and 2020 and began falling faster in mid-2020, well before generative AI accelerated the trend by absorbing developer questions that previously flowed to the site. Stack Overflow is a frequently cited case in studies of the 1% rule, contribution inequality in user-generated content, and the long-run sustainability of volunteer knowledge commons.