Trade Desk's stock jumps on S&P 500 inclusion as Ansys exits index due to acquisition

• The Trade Desk will replace Ansys in the S&P 500 effective Friday.
• Synopsys is expected to close its Ansys acquisition on Thursday.
• Trade Desk is joining the index a week after Datadog took Juniper Networks' spot.

Shares of The Trade Desk jumped 14% in extended trading on Monday, as the digital advertising company is set to to join the S&P 500.

S&P Global announced that Trade Desk will be replacing software maker Ansys as of Friday. Earlier on Monday, Synopsys said it “has received approval from all necessary authorities” to finalize its $35 billion acquisition of Ansys, which was announced last year, and expects the deal to close on or around Thursday.

Last week monitoring software company Datadog took Juniper Networks' place in the S&P 500 as part of the index's quarterly rebalancing. Most changes to the S&P 500 take place during the scheduled rebalancing. However, in the case of the closing of an acquisition, a company can be removed from the index and replaced off schedule.

Trade Desk has taken a big hit to its market cap this year, with the stock down 36% in 2025. That follows a 63% jump last year and 61% increase in 2023.

Stocks often rally when they're added to a major index, as fund managers need to rebalance their portfolios to reflect the changes. With a market cap of $37 billion, the company falls right about in the middle of the S&P 500 by valuation.

Founded in 2009 by CEO Jeff Green and David Pickles, Trade Desk went public on the Nasdaq in 2016. The company is based in Ventura, California, with over 3,522 employees as of Dec. 31. It competes against companies including Amazon and Google.