Reddit is joining the S&P 500. Here’s why that matters, and why the stock price is surging on the news

Shares of Reddit, Inc. (NYSE: RDDT) are experiencing a surge in premarket trading after S&P Dow Jones Indices announced the social media platform's inclusion in the prestigious S&P 500 Index. This news is providing a much-needed boost to RDDT shares. The S&P 500 is one of the three major stock indices in the United States, alongside the Dow and the Nasdaq-100.

Indices track how certain stocks are performing in the market, serving as a barometer for the economy's overall performance. The S&P 500 includes 500 major companies, making it a widely representative indicator of the broader U.S. economy. Reddit will join the S&P 500 as a result of the upcoming vacancy caused by the merger of real estate investment trust AvalonBay Communities, Inc. (NYSE: AVB) with Equity Residential (NYSE: EQR), forming a new company, Vivmark Residential (NYSE: VMRK).

This merger will leave the S&P 500 with just 499 companies, prompting S&P Dow Jones Indices to select Reddit to fill the vacancy. The company was chosen based on strict selection criteria, including financial viability, public float, adequate liquidity, and company type. Reddit's shares have responded positively to the news, surging by around 11.6% to $176.45 per share in premarket trading.

Although the addition of a company to the S&P 500 does not affect the company's financials, passive index funds and ETFs that track the S&P 500 are required to own shares in those companies. This forced buying creates demand, driving up the price of a single share. Before today's surge, Reddit shares had plunged more than 31% since the beginning of 2026, primarily due to concerns that Google's AI overviews, appearing at the top of all Google search results, might significantly dampen traffic to Reddit's website.