---
description: HTMLRewriter now supports streamed content for more efficient replacement of HTML elements
title: Transform HTML quickly with streaming content
image: https://developers.cloudflare.com/changelog/post/2025-01-31-html-rewriter-streaming/og.png?v=2d370a51de0a35a7
---

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January 31, 2025

## Transform HTML quickly with streaming content

[Workers](https://developers.cloudflare.com/workers/)

Copy as Markdown| [View as Markdown](https://developers.cloudflare.com/changelog/post/2025-01-31-html-rewriter-streaming/index.md)| [Agent setup](https://developers.cloudflare.com/agent-setup/)

You can now transform HTML elements with streamed content using [`HTMLRewriter`](https://developers.cloudflare.com/workers/runtime-apis/html-rewriter).

Methods like `replace`, `append`, and `prepend` now accept [`Response`](https://developers.cloudflare.com/workers/runtime-apis/response/) and [`ReadableStream`](https://developers.cloudflare.com/workers/runtime-apis/streams/readablestream/) values as [`Content`](https://developers.cloudflare.com/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.

*index.jsjs*

```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.tsts*

```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://developers.cloudflare.com/workers/runtime-apis/html-rewriter).

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