It was around midnight when Narita Naret received the alert, via the notification service she had paid for. The product she wanted was back in stock, and she knew that she had only minutes to act.

She rushed to open the website where the items were already in her shopping cart. Holding her breath, she clicked on the checkout button.

The screen loaded. Her purchase was successful.

Ms. Naret, 25, from Oregon, had not scored a pair of rare sneakers or a sought-after collectible. She had bought tea. Specifically: three small tins of high-quality matcha, the Japanese powdered green tea that has become scarce as a global craze snatches up the limited stock.

“It’s the same as Labubus,” Ms. Naret said of the matcha she bought this month, referring to the cult key-ring dolls that collectors line up for — and occasionally get into fights over.

Matcha has been growing in popularity worldwide for years, particularly among health-conscious consumers because of its potential benefits. But in the past year, demand has surged to dizzying levels, according to people in the industry, who attribute it in large part to internet buzz. The interest has caught tea farmers, manufacturers and sellers off guard, and driven fierce competition online among aficionados and resellers.

“Everyone is demanding it, especially on social media — TikTok, Instagram, everywhere,” said Matthew Youn, the owner of Maison Koko, an Australian wholesaler and retailer that sells about 11 tons of matcha annually.