A light-weight module that brings Fetch API to Node.js.
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Promise<[Response](#class-response)>
Perform an HTTP(S) fetch.
`url` should be an absolute URL, such as `https://example.com/`. A path-relative URL (`/file/under/root`) or protocol-relative URL (`//can-be-http-or-https.com/`) will result in a rejected `Promise`.
### Options
The default values are shown after each option key.
```js
{
// These properties are part of the Fetch Standard
method: 'GET',
headers: {}, // Request headers. format is the identical to that accepted by the Headers constructor (see below)
body: null, // Request body. can be null, or a Node.js Readable stream
redirect: 'follow', // Set to `manual` to extract redirect headers, `error` to reject redirect
signal: null, // Pass an instance of AbortSignal to optionally abort requests
// The following properties are node-fetch extensions
follow: 20, // maximum redirect count. 0 to not follow redirect
compress: true, // support gzip/deflate content encoding. false to disable
size: 0, // maximum response body size in bytes. 0 to disable
agent: null, // http(s).Agent instance or function that returns an instance (see below)
highWaterMark: 16384, // the maximum number of bytes to store in the internal buffer before ceasing to read from the underlying resource.
insecureHTTPParser: false // Use an insecure HTTP parser that accepts invalid HTTP headers when `true`.
}
```
#### Default Headers
If no values are set, the following request headers will be sent automatically:
| Header | Value |
| ------------------- | ------------------------------------------------------ |
| `Accept-Encoding` | `gzip, deflate, br` (when `options.compress === true`) |
| `Accept` | `*/*` |
| `Content-Length` | _(automatically calculated, if possible)_ |
| `Host` | _(host and port information from the target URI)_ |
| `Transfer-Encoding` | `chunked` _(when `req.body` is a stream)_ |
| `User-Agent` | `node-fetch` |
Note: when `body` is a `Stream`, `Content-Length` is not set automatically.
#### Custom Agent
The `agent` option allows you to specify networking related options which are out of the scope of Fetch, including and not limited to the following:
- Support self-signed certificate
- Use only IPv4 or IPv6
- Custom DNS Lookup
See [`http.Agent`](https://nodejs.org/api/http.html#http_new_agent_options) for more information.
If no agent is specified, the default agent provided by Node.js is used. Note that [this changed in Node.js 19](https://github.com/nodejs/node/blob/4267b92604ad78584244488e7f7508a690cb80d0/lib/_http_agent.js#L564) to have `keepalive` true by default. If you wish to enable `keepalive` in an earlier version of Node.js, you can override the agent as per the following code sample.
In addition, the `agent` option accepts a function that returns `http`(s)`.Agent` instance given current [URL](https://nodejs.org/api/url.html), this is useful during a redirection chain across HTTP and HTTPS protocol.
```js
import http from 'node:http';
import https from 'node:https';
const httpAgent = new http.Agent({
keepAlive: true
});
const httpsAgent = new https.Agent({
keepAlive: true
});
const options = {
agent: function(_parsedURL) {
if (_parsedURL.protocol == 'http:') {
return httpAgent;
} else {
return httpsAgent;
}
}
};
```
#### Custom highWaterMark
Stream on Node.js have a smaller internal buffer size (16kB, aka `highWaterMark`) from client-side browsers (>1MB, not consistent across browsers). Because of that, when you are writing an isomorphic app and using `res.clone()`, it will hang with large response in Node.
The recommended way to fix this problem is to resolve cloned response in parallel:
```js
import fetch from 'node-fetch';
const response = await fetch('https://example.com');
const r1 = response.clone();
const results = await Promise.all([response.json(), r1.text()]);
console.log(results[0]);
console.log(results[1]);
```
If for some reason you don't like the solution above, since `3.x` you are able to modify the `highWaterMark` option:
```js
import fetch from 'node-fetch';
const response = await fetch('https://example.com', {
// About 1MB
highWaterMark: 1024 * 1024
});
const result = await res.clone().arrayBuffer();
console.dir(result);
```
#### Insecure HTTP Parser
Passed through to the `insecureHTTPParser` option on http(s).request. See [`http.request`](https://nodejs.org/api/http.html#http_http_request_url_options_callback) for more information.
#### Manual Redirect
The `redirect: 'manual'` option for node-fetch is different from the browser & specification, which
results in an [opaque-redirect filtered response](https://fetch.spec.whatwg.org/#concept-filtered-response-opaque-redirect).
node-fetch gives you the typical [basic filtered response](https://fetch.spec.whatwg.org/#concept-filtered-response-basic) instead.
```js
import fetch from 'node-fetch';
const response = await fetch('https://httpbin.org/status/301', { redirect: 'manual' });
if (response.status === 301 || response.status === 302) {
const locationURL = new URL(response.headers.get('location'), response.url);
const response2 = await fetch(locationURL, { redirect: 'manual' });
console.dir(response2);
}
```
### Class: Request
An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the [Body](#iface-body) interface.
Due to the nature of Node.js, the following properties are not implemented at this moment:
- `type`
- `destination`
- `mode`
- `credentials`
- `cache`
- `integrity`
- `keepalive`
The following node-fetch extension properties are provided:
- `follow`
- `compress`
- `counter`
- `agent`
- `highWaterMark`
See [options](#fetch-options) for exact meaning of these extensions.
#### new Request(input[, options])
_(spec-compliant)_
- `input` A string representing a URL, or another `Request` (which will be cloned)
- `options` [Options](#fetch-options) for the HTTP(S) request
Constructs a new `Request` object. The constructor is identical to that in the [browser](https://developer.mozilla.org/en-US/docs/Web/API/Request/Request).
In most cases, directly `fetch(url, options)` is simpler than creating a `Request` object.
### Class: Response
An HTTP(S) response. This class implements the [Body](#iface-body) interface.
The following properties are not implemented in node-fetch at this moment:
- `trailer`
#### new Response([body[, options]])
_(spec-compliant)_
- `body` A `String` or [`Readable` stream][node-readable]
- `options` A [`ResponseInit`][response-init] options dictionary
Constructs a new `Response` object. The constructor is identical to that in the [browser](https://developer.mozilla.org/en-US/docs/Web/API/Response/Response).
Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a `Response` directly.
#### response.ok
_(spec-compliant)_
Convenience property representing if the request ended normally. Will evaluate to true if the response status was greater than or equal to 200 but smaller than 300.
#### response.redirected
_(spec-compliant)_
Convenience property representing if the request has been redirected at least once. Will evaluate to true if the internal redirect counter is greater than 0.
#### response.type
_(deviation from spec)_
Convenience property representing the response's type. node-fetch only supports `'default'` and `'error'` and does not make use of [filtered responses](https://fetch.spec.whatwg.org/#concept-filtered-response).
### Class: Headers
This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the [Fetch Standard][whatwg-fetch] are implemented.
#### new Headers([init])
_(spec-compliant)_
- `init` Optional argument to pre-fill the `Headers` object
Construct a new `Headers` object. `init` can be either `null`, a `Headers` object, an key-value map object or any iterable object.
```js
// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class
import {Headers} from 'node-fetch';
const meta = {
'Content-Type': 'text/xml'
};
const headers = new Headers(meta);
// The above is equivalent to
const meta = [['Content-Type', 'text/xml']];
const headers = new Headers(meta);
// You can in fact use any iterable objects, like a Map or even another Headers
const meta = new Map();
meta.set('Content-Type', 'text/xml');
const headers = new Headers(meta);
const copyOfHeaders = new Headers(headers);
```
### Interface: Body
`Body` is an abstract interface with methods that are applicable to both `Request` and `Response` classes.
#### body.body
_(deviation from spec)_
- Node.js [`Readable` stream][node-readable]
Data are encapsulated in the `Body` object. Note that while the [Fetch Standard][whatwg-fetch] requires the property to always be a WHATWG `ReadableStream`, in node-fetch it is a Node.js [`Readable` stream][node-readable].
#### body.bodyUsed
_(spec-compliant)_
- `Boolean`
A boolean property for if this body has been consumed. Per the specs, a consumed body cannot be used again.
#### body.arrayBuffer()
#### body.formData()
#### body.blob()
#### body.json()
#### body.text()
`fetch` comes with methods to parse `multipart/form-data` payloads as well as
`x-www-form-urlencoded` bodies using `.formData()` this comes from the idea that
Service Worker can intercept such messages before it's sent to the server to
alter them. This is useful for anybody building a server so you can use it to
parse & consume payloads.