Pinterest, Inc. (NYSE: PINS) is back in the spotlight on December 22, 2025—not because of a surprise earnings report, but because today is a “mechanical catalyst” day for the stock: Pinterest is officially being added to the S&P MidCap 400 as part of S&P Dow Jones Indices’ quarterly rebalance. ^[1]

At the same time, investors are digesting a busy December for the company, including its planned acquisition of connected-TV (CTV) ad platform tvScientific and a fresh round of Wall Street rating changes that highlight a familiar tug-of-war: Pinterest’s improving performance-ad story versus macro pressure in advertising budgets and intense competition from larger platforms.

As of the latest available trading update, PINS traded around…