The Trade Desk Inc. (TTD) will be added to the S&P 500 index, replacing Ansys Inc. (ANSS) effective before the market opens on Friday, July 18, 2025. This change follows Ansys' pending acquisition by Synopsys Inc. (SNPS), with the deal expected to close on July 17. The announcement of Trade Desk's inclusion in the benchmark index triggered a notable increase in its stock price, with shares rising between 11% and 15% in after-hours trading. The inclusion reflects a shift in the S&P 500's composition ahead of the trading session on July 18.