^{Getty Images}

The Trade Desk to Join S&P 500, Replacing Ansys After Synopsys Acquisition

Shares of digital advertising platform The Trade Desk jumped 14% in after-hours trading Monday, following the announcement that it will join the S&P 500 index, replacing software maker Ansys. The inclusion, effective this Friday, comes as Synopsys nears completion of its $35 billion acquisition of Ansys, expected to close on Thursday.

S&P Dow Jones Indices confirmed the index adjustment on Monday evening, citing the completion of the acquisition as the trigger for the off-cycle change. These types of changes typically occur during the S&P 500’s scheduled quarterly rebalancing, but major corporate events like mergers or takeovers can prompt earlier replacements.

Trade Desk Stock Rebounds After Tough Year

The inclusion comes at a crucial moment for The Trade Desk, which has seen its stock price decline by 36% year-to-date, wiping out a portion of the gains from the previous two years. The company surged 63% in 2024 and 61% in 2023, making it one of the standout tech performers during the post-pandemic digital advertising recovery.

Now with a market capitalization of roughly $37 billion, The Trade Desk sits comfortably in the middle tier of the S&P 500 constituents by valuation. The stock's surge after the S&P announcement reflects the common market dynamic where funds tracking the index must buy shares of newly added companies to stay aligned with the benchmark.

Background: Ansys Exits, Synopsys Expands

Ansys, the engineering simulation software giant being acquired, will be removed from the S&P 500 following the expected completion of its all-cash-and-stock transaction with Synopsys. The $35 billion deal, first announced in early 2024, recently cleared all necessary regulatory approvals across multiple jurisdictions.

Synopsys, a leader in electronic design automation (EDA), is expected to significantly expand its reach through the Ansys integration, combining simulation and chip design tools to compete more aggressively in semiconductor innovation and R&D-heavy industries.

The closing of the deal is scheduled for Thursday, clearing the path for The Trade Desk’s entry into the index on Friday.

A Growing Presence in Digital Advertising

Founded in 2009 by Jeff Green and David Pickles, The Trade Desk went public in 2016 and is headquartered in Ventura, California. As of the end of 2024, the company employed over 3,500 people globally.

The Trade Desk operates a demand-side platform (DSP) that allows advertisers to purchase digital ad inventory in real time across channels such as display, video, connected TV, and audio. It is considered one of the key independent players in programmatic advertising and competes with giants like Google, Amazon, and Meta, all of which have increasingly invested in their advertising ecosystems.

Despite a challenging 2025 so far, The Trade Desk has retained investor confidence thanks to its focus on transparent data practices, robust partnerships with media companies, and leadership in the growing connected TV ad market.

Index Inclusions Trigger Institutional Demand

Being added to the S&P 500 often leads to a short-term boost in share price due to increased demand from index-tracking funds and institutional investors. According to a 2023 study from JPMorgan Asset Management, stocks added to the S&P 500 experience an average 5–10% price increase in the days following inclusion, largely driven by passive portfolio rebalancing.

Last week, Datadog replaced Juniper Networks in a similar reshuffling, part of a wave of S&P 500 changes influenced by M&A activity and market cap shifts.

Outlook: More Than Just a Symbolic Win

While inclusion in the S&P 500 is symbolic of a company’s size and market significance, it also brings real capital inflows and increased visibility. For The Trade Desk, this milestone may help stabilize its stock after a volatile year and provide a runway for renewed investor interest as it continues to expand in a highly competitive digital ad landscape.

With Ansys exiting and The Trade Desk entering, this reshuffling highlights the dynamic nature of today’s tech sector — where innovation, consolidation, and investor sentiment continue to drive rapid change.