MIT License

Copyright (c) Matteo Collina and Undici contributors

Permission is hereby granted, free of charge, to any person obtaining a copy

of this software and associated documentation files (the "Software"), to deal

in the Software without restriction, including without limitation the rights

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

copies of the Software, and to permit persons to whom the Software is

furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all

copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

SOFTWARE.

[](https://github.com/nodejs/undici/actions/workflows/nodejs.yml) [](http://standardjs.com/) [](https://badge.fury.io/js/undici) [](https://codecov.io/gh/nodejs/undici)

A HTTP/1.1 client, written from scratch for Node.js.

It is also a Stranger Things reference.

Have a question about using Undici? Open a [Q&A Discussion](https://github.com/nodejs/undici/discussions/new) or join our official OpenJS [Slack](https://openjs-foundation.slack.com/archives/C01QF9Q31QD) channel.

The benchmark is a simple `hello world` [example](benchmarks/benchmark.js) using a

number of unix sockets (connections) with a pipelining depth of 10 running on Node 16.

The benchmarks below have the [simd](https://github.com/WebAssembly/simd) feature enabled.

| Tests | Samples | Result | Tolerance | Difference with slowest |

|---------------------|---------|---------------|-----------|-------------------------|

| http - no keepalive | 15 | 4.63 req/sec | ± 2.77 % | - |

| http - keepalive | 10 | 4.81 req/sec | ± 2.16 % | + 3.94 % |

| undici - stream | 25 | 62.22 req/sec | ± 2.67 % | + 1244.58 % |

| undici - dispatch | 15 | 64.33 req/sec | ± 2.47 % | + 1290.24 % |

| undici - request | 15 | 66.08 req/sec | ± 2.48 % | + 1327.88 % |

| undici - pipeline | 10 | 66.13 req/sec | ± 1.39 % | + 1329.08 % |

| Tests | Samples | Result | Tolerance | Difference with slowest |

|---------------------|---------|------------------|-----------|-------------------------|

| http - no keepalive | 50 | 3546.49 req/sec | ± 2.90 % | - |

| http - keepalive | 15 | 5692.67 req/sec | ± 2.48 % | + 60.52 % |

| undici - pipeline | 25 | 8478.71 req/sec | ± 2.62 % | + 139.07 % |

| undici - request | 20 | 9766.66 req/sec | ± 2.79 % | + 175.39 % |

| undici - stream | 15 | 10109.74 req/sec | ± 2.94 % | + 185.06 % |

| undici - dispatch | 25 | 10949.73 req/sec | ± 2.54 % | + 208.75 % |

import { request } from 'undici'

const {

statusCode,

headers,

trailers,

body

} = await request('http://localhost:3000/foo')

console.log('response received', statusCode)

console.log('headers', headers)

for await (const data of body) {

console.log('data', data)

}

console.log('trailers', trailers)

Using [the body mixin from the Fetch Standard](https://fetch.spec.whatwg.org/#body-mixin).

import { request } from 'undici'

const {

statusCode,

headers,

trailers,

body

} = await request('http://localhost:3000/foo')

console.log('response received', statusCode)

console.log('headers', headers)

console.log('data', await body.json())

console.log('trailers', trailers)

This section documents our most commonly used API methods. Additional APIs are documented in their own files within the [docs](./docs/) folder and are accessible via the navigation list on the left side of the docs site.

Arguments:

* **url** `string | URL | UrlObject`

* **options** [`RequestOptions`](./docs/api/Dispatcher.md#parameter-requestoptions)

* **dispatcher** `Dispatcher` - Default: [getGlobalDispatcher](#undicigetglobaldispatcher)

* **method** `String` - Default: `PUT` if `options.body`, otherwise `GET`

* **maxRedirections** `Integer` - Default: `0`

Returns a promise with the result of the `Dispatcher.request` method.

Calls `options.dispatcher.request(options)`.

See [Dispatcher.request](./docs/api/Dispatcher.md#dispatcherrequestoptions-callback) for more details.

Arguments:

* **url** `string | URL | UrlObject`

* **options** [`StreamOptions`](./docs/api/Dispatcher.md#parameter-streamoptions)

* **dispatcher** `Dispatcher` - Default: [getGlobalDispatcher](#undicigetglobaldispatcher)

* **method** `String` - Default: `PUT` if `options.body`, otherwise `GET`

* **maxRedirections** `Integer` - Default: `0`

* **factory** `Dispatcher.stream.factory`

Returns a promise with the result of the `Dispatcher.stream` method.

Calls `options.dispatcher.stream(options, factory)`.

See [Dispatcher.stream](docs/api/Dispatcher.md#dispatcherstreamoptions-factory-callback) for more details.

Arguments:

* **url** `string | URL | UrlObject`

* **options** [`PipelineOptions`](docs/api/Dispatcher.md#parameter-pipelineoptions)

* **dispatcher** `Dispatcher` - Default: [getGlobalDispatcher](#undicigetglobaldispatcher)

* **method** `String` - Default: `PUT` if `options.body`, otherwise `GET`

* **maxRedirections** `Integer` - Default: `0`

* **handler** `Dispatcher.pipeline.handler`

Returns: `stream.Duplex`

Calls `options.dispatch.pipeline(options, handler)`.

See [Dispatcher.pipeline](docs/api/Dispatcher.md#dispatcherpipelineoptions-handler) for more details.

Starts two-way communications with the requested resource using [HTTP CONNECT](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/CONNECT).

Arguments:

* **url** `string | URL | UrlObject`

* **options** [`ConnectOptions`](docs/api/Dispatcher.md#parameter-connectoptions)

* **dispatcher** `Dispatcher` - Default: [getGlobalDispatcher](#undicigetglobaldispatcher)

* **maxRedirections** `Integer` - Default: `0`

* **callback** `(err: Error | null, data: ConnectData | null) => void` (optional)

Returns a promise with the result of the `Dispatcher.connect` method.

Calls `options.dispatch.connect(options)`.

See [Dispatcher.connect](docs/api/Dispatcher.md#dispatcherconnectoptions-callback) for more details.

Implements [fetch](https://fetch.spec.whatwg.org/#fetch-method).

* https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch

* https://fetch.spec.whatwg.org/#fetch-method

Only supported on Node 16.5+.

This is [experimental](https://nodejs.org/api/documentation.html#documentation_stability_index) and is not yet fully compliant with the Fetch Standard.

We plan to ship breaking changes to this feature until it is out of experimental.

Help us improve the test coverage by following instructions at [nodejs/undici/#951](https://github.com/nodejs/undici/issues/951).

Basic usage example:

import {fetch} from 'undici';

async function fetchJson() {

const res = await fetch('https://example.com')

const json = await res.json()

console.log(json);

}

A body can be of the following types:

- ArrayBuffer

- ArrayBufferView

- AsyncIterables

- Blob

- Iterables

- String

- URLSearchParams

- FormData

In this implementation of fetch, ```request.body``` now accepts ```Async Iterables```. It is not present in the [Fetch Standard.](https://fetch.spec.whatwg.org)

import { fetch } from "undici";

const data = {

async *[Symbol.asyncIterator]() {

yield "hello";

yield "world";

},

};

(async () => {

await fetch("https://example.com", { body: data, method: 'POST' });

})();

Nodejs has two kinds of streams: [web streams](https://nodejs.org/dist/latest-v16.x/docs/api/webstreams.html) which follow the API of the WHATWG web standard found in browsers, and an older Node-specific [streams API](https://nodejs.org/api/stream.html). `response.body` returns a readable web stream. If you would prefer to work with a Node stream you can convert a web stream using `.fromWeb()`.

import {fetch} from 'undici';

import {Readable} from 'node:stream';

async function fetchStream() {

const response = await fetch('https://example.com')

const readableWebStream = response.body;

const readableNodeStream = Readable.fromWeb(readableWebStream);

}

This section documents parts of the [Fetch Standard](https://fetch.spec.whatwg.org) which Undici does

not support or does not fully implement.

* https://fetch.spec.whatwg.org/#garbage-collection

The [Fetch Standard](https://fetch.spec.whatwg.org) allows users to skip consuming the response body by relying on

[garbage collection](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Memory_Management#garbage_collection) to release connection resources. Undici does not do the same. Therefore, it is important to always either consume or cancel the response body.

Garbage collection in Node is less aggressive and deterministic

(due to the lack of clear idle periods that browser have through the rendering refresh rate)

which means that leaving the release of connection resources to the garbage collector can lead

to excessive connection usage, reduced performance (due to less connection re-use), and even

stalls or deadlocks when running out of connections.

const headers = await fetch(url)

.then(async res => {

for await (const chunk of res.body) {

// force consumption of body

}

return res.headers

})

const headers = await fetch(url)

.then(res => res.headers)

Upgrade to a different protocol. See [MDN - HTTP - Protocol upgrade mechanism](https://developer.mozilla.org/en-US/docs/Web/HTTP/Protocol_upgrade_mechanism) for more details.

Arguments:

* **url** `string | URL | UrlObject`

* **options** [`UpgradeOptions`](docs/api/Dispatcher.md#parameter-upgradeoptions)

* **dispatcher** `Dispatcher` - Default: [getGlobalDispatcher](#undicigetglobaldispatcher)

* **maxRedirections** `Integer` - Default: `0`

* **callback** `(error: Error | null, data: UpgradeData) => void` (optional)

Returns a promise with the result of the `Dispatcher.upgrade` method.

Calls `options.dispatcher.upgrade(options)`.

See [Dispatcher.upgrade](docs/api/Dispatcher.md#dispatcherupgradeoptions-callback) for more details.

* dispatcher `Dispatcher`

Sets the global dispatcher used by Common API Methods.

Gets the global dispatcher used by Common API Methods.

Returns: `Dispatcher`

* **port** `string | number` (optional)

* **path** `string` (optional)

* **pathname** `string` (optional)

* **hostname** `string` (optional)

* **origin** `string` (optional)

* **protocol** `string` (optional)

* **search** `string` (optional)

This section documents parts of the HTTP/1.1 specification which Undici does

not support or does not fully implement.

Undici does not support the `Expect` request header field. The request

body is always immediately sent and the `100 Continue` response will be

ignored.

Refs: https://tools.ietf.org/html/rfc7231#section-5.1.1

Undici will only use pipelining if configured with a `pipelining` factor

greater than `1`.

Undici always assumes that connections are persistent and will immediately

pipeline requests, without checking whether the connection is persistent.

Hence, automatic fallback to HTTP/1.0 or HTTP/1.1 without pipelining is

not supported.

Undici will immediately pipeline when retrying requests after a failed

connection. However, Undici will not retry the first remaining requests in

the prior pipeline and instead error the corresponding callback/promise/stream.

Undici will abort all running requests in the pipeline when any of them are

aborted.

* Refs: https://tools.ietf.org/html/rfc2616#section-8.1.2.2

* Refs: https://tools.ietf.org/html/rfc7230#section-6.3.2

Since it is not possible to manually follow an HTTP redirect on server-side,

Undici returns the actual response instead of an `opaqueredirect` filtered one

when invoked with a `manual` redirect. This aligns `fetch()` with the other

implementations in Deno and Cloudflare Workers.

Refs: https://fetch.spec.whatwg.org/#atomic-http-redirect-handling

* [__Daniele Belardi__](https://github.com/dnlup), <https://www.npmjs.com/~dnlup>

* [__Ethan Arrowood__](https://github.com/ethan-arrowood), <https://www.npmjs.com/~ethan_arrowood>

* [__Matteo Collina__](https://github.com/mcollina), <https://www.npmjs.com/~matteo.collina>

* [__Robert Nagy__](https://github.com/ronag), <https://www.npmjs.com/~ronag>

* [__Szymon Marczak__](https://github.com/szmarczak), <https://www.npmjs.com/~szmarczak>

* [__Tomas Della Vedova__](https://github.com/delvedor), <https://www.npmjs.com/~delvedor>

* [__Ethan Arrowood__](https://github.com/ethan-arrowood), <https://www.npmjs.com/~ethan_arrowood>

* [__Matteo Collina__](https://github.com/mcollina), <https://www.npmjs.com/~matteo.collina>

* [__Robert Nagy__](https://github.com/ronag), <https://www.npmjs.com/~ronag>

MIT