React 19.3 adds browser() API for opting out of server rendering

React 19.3 shipped on npm on September 9 alongside stable View Transitions and Fragment Refs. The new react-dom browser() API lets a component formally opt out of server-side rendering: on the server use(browser()) suspends the component and leaves the nearest Suspense fallback, while in the browser it returns undefined.

• browser() must be called from a Client Component inside a Suspense boundary
• On the server use(browser()) leaves the fallback; in the browser it returns undefined
• New onBrowserBailout callback and optional reason argument were added
• The API is still flagged as Canary only