Streaming SSR

Summary

Send HTML shell early, stream completed segments as async data resolves — improves TTFB vs buffer-all SSR. Suspense boundaries map to stream chunks. Reverse proxies must not buffer entire response. Error mid-stream needs fallback HTML and status handling.

Code example

import { renderToReadableStream } from 'react-dom/server';

const stream = await renderToReadableStream(<App />, {
  bootstrapScripts: ['/client.js'],
});

return new Response(stream, {
  headers: { 'Content-Type': 'text/html' },
});

Key points

• Send HTML shell early, stream completed segments as async data resolves — improves TTFB vs buffer-all SSR.
• Suspense boundaries map to stream chunks.
• Reverse proxies must not buffer entire response.
• Error mid-stream needs fallback HTML and status handling.

Further reading

• Streaming SSR
• Streaming HTML

Related concepts

• Partial hydration
• Shadow DOM