---
title: Transform HTML quickly with streaming content
description: HTMLRewriter now supports streamed content for more efficient replacement of HTML elements
image: https://edgetunnel-b2h.pages.dev/changelog-preview.png
---

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# Changelog

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## Transform HTML quickly with streaming content

Jan 31, 2025 

[ Workers ](https://edgetunnel-b2h.pages.dev/workers/) 

You can now transform HTML elements with streamed content using [HTMLRewriter](https://edgetunnel-b2h.pages.dev/workers/runtime-apis/html-rewriter).

Methods like `replace`, `append`, and `prepend` now accept [Response](https://edgetunnel-b2h.pages.dev/workers/runtime-apis/response/) and [ReadableStream](https://edgetunnel-b2h.pages.dev/workers/runtime-apis/streams/readablestream/)values as [Content](https://edgetunnel-b2h.pages.dev/workers/runtime-apis/html-rewriter/#global-types).

This can be helpful in a variety of situations. For instance, you may have a Worker in front of an origin, and want to replace an element with content from a different source. Prior to this change, you would have to load all of the content from the upstream URL and convert it into a string before replacing the element. This slowed down overall response times.

Now, you can pass the `Response` object directly into the `replace` method, and HTMLRewriter will immediately start replacing the content as it is streamed in. This makes responses faster.

* [  JavaScript ](#tab-panel-2945)
* [  TypeScript ](#tab-panel-2946)

**index.js**

```js
class ElementRewriter {
  async element(element) {
    // able to replace elements while streaming content
    // the fetched body is not buffered into memory as part
    // of the replace
    let res = await fetch("https://upstream-content-provider.example");
    element.replace(res);
  }
}


export default {
  async fetch(request, env, ctx) {
    let response = await fetch("https://site-to-replace.com");
    return new HTMLRewriter()
      .on("[data-to-replace]", new ElementRewriter())
      .transform(response);
  },
};
```

**index.ts**

```ts
class ElementRewriter {
  async element(element: any) {
    // able to replace elements while streaming content
    // the fetched body is not buffered into memory as part
    // of the replace
    let res = await fetch('https://upstream-content-provider.example');
    element.replace(res);
  }
}


export default {
  async fetch(request, env, ctx): Promise<Response> {
    let response = await fetch('https://site-to-replace.com');
    return new HTMLRewriter().on('[data-to-replace]', new ElementRewriter()).transform(response);
  },
} satisfies ExportedHandler<Env>;
```

For more information, see the [HTMLRewriter documentation](https://edgetunnel-b2h.pages.dev/workers/runtime-apis/html-rewriter).

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```