---
title: Streaming HTTP Server with Async Iterators
sidebarTitle: Stream with iterators
mode: center
---

In Bun, a [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response) accepts an async generator function as its body, so you can stream data to the client as it becomes available rather than waiting for the entire response to be ready.

```ts stream-iterator.ts icon="/icons/typescript.svg"
Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response(
      // An async generator function
      async function* () {
        yield "Hello, ";
        await Bun.sleep(100);
        yield "world!";

        // you can also yield a TypedArray or Buffer
        yield new Uint8Array(["\n".charCodeAt(0)]);
      },
      { headers: { "Content-Type": "text/plain" } },
    );
  },
});
```

---

You can pass any async iterable directly to `Response`:

```ts stream-iterator.ts icon="/icons/typescript.svg"
Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response(
      {
        [Symbol.asyncIterator]: async function* () {
          yield "Hello, ";
          await Bun.sleep(100);
          yield "world!";
        },
      },
      { headers: { "Content-Type": "text/plain" } },
    );
  },
});
```
