---
title: Streams
description: Use the Node.js streams API in Cloudflare Workers for readable, writable, and transform stream operations.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Streams

Note

To enable built-in Node.js APIs and polyfills, add the nodejs\_compat compatibility flag to your [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/configuration/). This also enables nodejs\_compat\_v2 as long as your compatibility date is 2024-09-23 or later. [Learn more about the Node.js compatibility flag and v2](https://developers.cloudflare.com/workers/configuration/compatibility-flags/#nodejs-compatibility-flag).

The [Node.js streams API ↗](https://nodejs.org/api/stream.html) is the original API for working with streaming data in JavaScript, predating the [WHATWG ReadableStream standard ↗](https://streams.spec.whatwg.org/). A stream is an abstract interface for working with streaming data in Node.js. Streams can be readable, writable, or both. All streams are instances of [EventEmitter](https://developers.cloudflare.com/workers/runtime-apis/nodejs/eventemitter/).

Where possible, you should use the [WHATWG standard "Web Streams" API ↗](https://streams.spec.whatwg.org/), which is [supported in Workers ↗](https://streams.spec.whatwg.org/).

JavaScript

```

import { Readable, Transform } from "node:stream";


import { text } from "node:stream/consumers";


import { pipeline } from "node:stream/promises";


// A Node.js-style Transform that converts data to uppercase

// and appends a newline to the end of the output.

class MyTransform extends Transform {

  constructor() {

    super({ encoding: "utf8" });

  }

  _transform(chunk, _, cb) {

    this.push(chunk.toString().toUpperCase());

    cb();

  }

  _flush(cb) {

    this.push("\n");

    cb();

  }

}


export default {

  async fetch() {

    const chunks = [

      "hello ",

      "from ",

      "the ",

      "wonderful ",

      "world ",

      "of ",

      "node.js ",

      "streams!",

    ];


    function nextChunk(readable) {

      readable.push(chunks.shift());

      if (chunks.length === 0) readable.push(null);

      else queueMicrotask(() => nextChunk(readable));

    }


    // A Node.js-style Readable that emits chunks from the

    // array...

    const readable = new Readable({

      encoding: "utf8",

      read() {

        nextChunk(readable);

      },

    });


    const transform = new MyTransform();

    await pipeline(readable, transform);

    return new Response(await text(transform));

  },

};


```

Refer to the [Node.js documentation for stream ↗](https://nodejs.org/api/stream.html) for more information.

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/workers/","name":"Workers"}},{"@type":"ListItem","position":3,"item":{"@id":"/workers/runtime-apis/","name":"Runtime APIs"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers/runtime-apis/nodejs/","name":"Node.js compatibility"}},{"@type":"ListItem","position":5,"item":{"@id":"/workers/runtime-apis/nodejs/streams/","name":"Streams"}}]}
```