(Reuters) -Pinterest ( PINS ) forecast fourth-quarter revenue slightly below Wall Street estimates on Tuesday, signaling fierce competition from larger platforms such as Meta during the holiday shopping season, sending its shares down over 15% in extended trading.

The company expects quarterly revenue between $1.31 billion and $1.34 billion, with the midpoint marginally below analysts' average estimate of $1.34 billion, according to data compiled by LSEG.

Pinterest's ( PINS ) results follow reports from digital ad bellwethers, including Google-parent Alphabet, Meta and Reddit ( RDDT ), which posted upbeat third-quarter revenue on robust ad spending.

Large platforms such as TikTok and Meta's Instagram and Facebook remain the top choices for marketers, thanks to their massive user bases and sophisticated artificial intelligence tools for campaign creation.

The image sharing platform also offers an AI-powered Performance+ ad suite to marketers for creating personalized and automated campaigns.

Pinterest ( PINS ) had said it saw lower spending by Asia-based e-commerce retailers in the U.S. after the end of the "de minimis" exemption, though some shifted budgets to Europe and other regions.

The end of the U.S. duty-free import provision for low-value shipments from China and Hong Kong has prompted some Chinese retailers, such as Temu and Shein, to adjust their marketing budgets.

Pinterest's ( PINS ) global monthly active users are rising, with the company hitting an all-time high of 600 million in the third quarter.

The company's revenue grew 17% to $1.05 billion in the third quarter, aligning with analysts' estimates and marking its return to the billion-dollar revenue level first attained in the holiday quarter of 2024.

Adjusted profit per share came in at 38 cents for the quarter ended September 30, missing estimates of 42 cents.