How does the Next.js App Router handle large JSON payloads compared to the Pages Router?

Next.js App Router handles JSON differently through React Server Components, reducing client-side payload compared to Pages Router. App Router sends rendered UI instead of raw JSON data, significantly decreasing bundle size. Server Components fetch data server-side without including fetch logic or JSON in client bundle. Pages Router includes getServerSideProps data in initial page JSON, increasing payload. App Router streaming allows progressive rendering, sending UI chunks as data arrives. Pages Router sends complete JSON before rendering starts. For large datasets, App Router is dramatically more efficient, sometimes reducing payload by 70-80%. However, App Router requires thoughtful client/server boundary decisions. Client Components still receive full JSON if fetched client-side. Use Server Components for data fetching to minimize payload. Pages Router is simpler for straightforward data passing but less efficient. Test payload sizes in Network tab comparing both approaches. Validate JSON structure with our JSON Formatter at jsonconsole.com/json-formatter regardless of router choice. App Router excels with large, complex JSON through selective hydration and streaming, making it superior for data-heavy applications.