Reddit filed an S-1 form with the SEC ahead of its planned IPO, revealing its largest shareholders. OpenAI CEO Sam Altman owns an 8.7% stake in Reddit, making him the company's third-largest shareholder. This is a new disclosure, as Altman's exact ownership was previously unknown despite being known as a Reddit investor. Advance, owned by the Newhouse family, controls 30% of Reddit shares, while Tencent owns 11%. Altman previously served seven years on Reddit's board until 2022. AI may be a key revenue source, as Reddit inked a $60 million per year deal giving Google access to its user-generated content.