Understanding React Server Components (RSC) in Next.js 15

The Shift to the Server

React Server Components change the default mental model of React. Components now render on the server by default, sending zero JS to the client.

Streaming HTML

Next.js 15 leverages HTTP streaming to send parts of the UI as they become ready. This significantly lowers Time To First Byte (TTFB).

When to use "use client"?

Only use client components when you need interactivity (onClick, useState, useEffect). Keep your leaves interactive and your trunk static.