How Oura’s rings found their way onto millions of fingers

Oura built its business around the idea that rings can track health data more discreetly and accurately than wrist devices. The company’s hardware has become slimmer, its app turns the data into personalised guidance, and subscriptions now provide a fifth of revenue with 5m members. Oura reported $1.2bn in nine-month sales and filed for a US IPO at a reported valuation above $16bn. Smart rings remain far smaller than wristbands and smartwatches, but rapid growth is attracting rivals and could draw Apple into the category.