Rewriter API

if ('Rewriter' in self) {
  // The Rewriter API is supported.
}

const availability = await Rewriter.availability();

const rewriter = await Rewriter.create({
  monitor(m) {
    m.addEventListener("downloadprogress", e => {
      console.log(`Downloaded ${e.loaded * 100}%`);
    });
  }
});

const options = {
  sharedContext: 'This is an email to acquaintances about an upcoming event.',
  tone: 'more-casual',
  format: 'plain-text',
  length: 'shorter',
};

const available = await Rewriter.availability();
let rewriter;
if (available === 'unavailable') {
  // The Rewriter API isn't usable.
  return;
}
if (available === 'available') {
  // The Rewriter API can be used immediately .
  rewriter = await Rewriter.create(options);
} else {
  // The Rewriter can be used after the model is downloaded.
  rewriter = await Rewriter.create(options);
  rewriter.addEventListener('downloadprogress', (e) => {
    console.log(e.loaded, e.total);
  });
}

const rewriter = await Rewriter.create({
  tone: "more-formal",
  expectedInputLanguages: ["en", "ja", "es"],
  expectedContextLanguages: ["en", "ja", "es"],
  outputLanguage: "es",
  sharedContext: "These are requests to rewrite messages to teachers in a
    Spanish language program, by students who may speak Spanish, Japanese, or
    English. Staff expect questions to be written in Spanish."
});

// Request-based
const rewriter = await Rewriter.create({
  sharedContext: "A review for the Flux Capacitor 3000 from TimeMachines Inc."
});
const result = await rewriter.rewrite(reviewEl.textContent, {
  context: "Avoid any toxic language and be as constructive as possible."
});

const rewriter = await Rewriter.create({
  sharedContext: "A review for the Flux Capacitor 3000 from TimeMachines Inc."
});

const stream = rewriter.rewriteStreaming(reviewEl.textContent, {
  context: "Avoid any toxic language and be as constructive as possible.",
  tone: "more-casual",
});

for await (const chunk of stream) {
  composeTextbox.append(chunk);
}

// Shared context and per writing task context
const rewriter = await Rewriter.create({
  sharedContext: "This is for publishing on [popular website name], a business and employment-focused social media platform."
});

const stream = rewriter.rewriteStreaming(
  "Love all this work on generative AI at Google! So much to learn and so many new things I can do!",
  {
    context: "The request comes from someone working at a startup providing an e-commerce CMS solution.",
    tone: "more-casual",
  }
);

for await (const chunk of stream) {
  composeTextbox.append(chunk);
}

// Reusing a rewriter
const rewriter = await Rewriter.create({
  sharedContext: "A review for the Flux Capacitor 3000 from TimeMachines Inc."
});

const rewrittenReviews = await Promise.all(
  Array.from(
    document.querySelectorAll("#reviews > .review"),
    (reviewEl) => rewriter.rewrite(reviewEl.textContent, {
      context: "Avoid any toxic language and be as constructive as possible.",
      tone: "more-casual",
    })
  ),
);

// Stop a rewriter
const controller = new AbortController();
stopButton.onclick = () => controller.abort();

const rewriter = await Rewriter.create({ signal: controller.signal });
await rewriter.rewrite(reviewEl.textContent, { signal: controller.signal });

// Destroy a rewriter
rewriter.destroy();

<!--
  The hosting site at https://main.example.com can grant a cross-origin iframe
  at https://cross-origin.example.com/ access to the Rewriter API by
  setting the `allow="rewriter"` attribute.
-->
<iframe src="https://cross-origin.example.com/" allow="rewriter"></iframe>