React 19 use() Hook: Guide to Promises and Context

Introduction React 19, stable since December 2024, introduced one of the most significant API additions in the library's history: use(). After more than a year in production across thousands of applications, use() has fundamentally changed how React developers think about data fetching, asynchronous operations, and context consumption. For years, the standard pattern for data fetching in React looked something like this: mount the component, fire off a useEffect, manage loading and error states with useState, and deal with cleanup and race conditions manually. Every component that needed server data repeated this same boilerplate. The result was verbose code, request waterfalls where child components had to wait for parents to render before initiating their own fetches, and an inconsistent user experience as different developers handled loading and error states differently. The use() API solves these problems by letting you read the value of a resource -- specifically a Promise or a Co