v148 · HTML · JavaScript · Declarative Partial Updates

Streaming Feed

Pipe a ReadableStream of HTML directly into a DOM element using streamHTMLUnsafe(). Content renders as chunks arrive — the same progressive parsing as the main HTML document, but for any element, at any time.

Chrome 148 flag required: This demo uses streamHTMLUnsafe() when available (Chrome 148+ with chrome://flags/#enable-experimental-web-platform-features). In other browsers it falls back to a polyfill that buffers and applies on completion, so you'll see the same result without the progressive rendering.
method —
chunks received 0
bytes 0
status idle
Hit "Stream articles" to start streaming HTML into this element

Before — innerHTML (blocks)

const res = await fetch('/api/feed.html');
const html = await res.text(); // wait for ALL bytes
// Only now can we set the content
target.innerHTML = html;

Chrome 148 — streamHTMLUnsafe

const res = await fetch('/api/feed.html');
const writer = target.streamHTMLUnsafe().getWriter();

// Or pipe directly:
res.body
  .pipeThrough(new TextDecoderStream())
  .pipeTo(target.streamHTMLUnsafe());

Full demo code

async function streamArticles(target, speedMs) {
  // Build a ReadableStream of HTML chunks
  const stream = new ReadableStream({
    async start(controller) {
      for (const article of ARTICLES) {
        const html = renderArticle(article);
        controller.enqueue(html);
        await delay(speedMs);
      }
      controller.close();
    }
  });

  if ('streamHTMLUnsafe' in target) {
    // Chrome 148+: pipe straight in, renders progressively
    await stream.pipeTo(target.streamHTMLUnsafe());
  } else {
    // Fallback: buffer then set
    const reader = stream.getReader();
    let full = '';
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      full += value;
    }
    target.innerHTML = full;
  }
}

see also

implementation reference

Need the exact API surface, compatibility boundaries, errors, lifecycle, and source links? Read the matching gendn reference ↗