Streaming

Overview

docxio supports streaming .docx bytes as a ReadableStream, which is useful for HTTP responses where you want to start sending data before the entire document is assembled.

renderToStream

import { renderToStream } from "docxio";

const stream = renderToStream(
  <document title="Streamed Report">
    <section>
      <paragraph><run>Hello from a stream!</run></paragraph>
    </section>
  </document>
);

The returned stream is a standard web ReadableStream<Uint8Array>.

HTTP response (Bun)

import { renderToStream } from "docxio";

Bun.serve({
  fetch(req) {
    const doc = (
      <document title="Report">
        <section>
          <paragraph><run>Generated on the fly.</run></paragraph>
        </section>
      </document>
    );

    const stream = renderToStream(doc);

    return new Response(stream, {
      headers: {
        "Content-Type":
          "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
        "Content-Disposition": 'attachment; filename="report.docx"',
      },
    });
  },
});

HTTP response (Node.js / Express)

import { renderToReadableStream } from "docxio";
import { Readable } from "node:stream";

app.get("/report.docx", async (req, res) => {
  const doc = (
    <document title="Report">
      <section>
        <paragraph><run>Server-generated document.</run></paragraph>
      </section>
    </document>
  );

  const webStream = renderToReadableStream(doc);
  const nodeStream = Readable.fromWeb(webStream);

  res.setHeader(
    "Content-Type",
    "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
  );
  res.setHeader("Content-Disposition", 'attachment; filename="report.docx"');
  nodeStream.pipe(res);
});

When to use streaming

Streaming is beneficial when:

• The document is large and you want to reduce time-to-first-byte
• You are serving documents over HTTP and want to avoid buffering the entire file in memory
• You are piping directly to a file or another stream consumer

For small documents or when you need the complete bytes (e.g., to calculate a hash), use render() instead.