A light-weight module that brings Fetch API to Node.js.
Consider supporting us on our Open Collective:
You might be looking for the v2 docs
- Motivation
- Features
- Difference from client-side fetch
- Installation
- Loading and configuring the module
- Upgrading
- Common Usage
- Advanced Usage
- API
- TypeScript
- Acknowledgement
- Team - Former
- License
Instead of implementing XMLHttpRequest in Node.js to run browser-specific Fetch polyfill, why not go from native http to fetch API directly? Hence, node-fetch, minimal code for a window.fetch compatible API on Node.js runtime.
See Jason Miller's isomorphic-unfetch or Leonardo Quixada's cross-fetch for isomorphic usage (exports node-fetch for server-side, whatwg-fetch for client-side).
- Stay consistent with
window.fetchAPI. - Make conscious trade-off when following WHATWG fetch spec and stream spec implementation details, document known differences.
- Use native promise and async functions.
- Use native Node streams for body, on both request and response.
- Decode content encoding (gzip/deflate/brotli) properly, and convert string output (such as
res.text()andres.json()) to UTF-8 automatically. - Useful extensions such as redirect limit, response size limit, explicit errors for troubleshooting.
- See known differences:
- If you happen to use a missing feature that
window.fetchoffers, feel free to open an issue. - Pull requests are welcomed too!
Current stable release (3.x) requires at least Node.js 12.20.0.
npm install node-fetchimport fetch from 'node-fetch';node-fetch from v3 is an ESM-only module - you are not able to import it with require().
If you cannot switch to ESM, please use v2 which remains compatible with CommonJS. Critical bug fixes will continue to be published for v2.
npm install node-fetch@2Alternatively, you can use the async import() function from CommonJS to load node-fetch asynchronously:
// mod.cjs
const fetch = (...args) => import('node-fetch').then(({default: fetch}) => fetch(...args));To use fetch() without importing it, you can patch the global object in node:
// fetch-polyfill.js
import fetch, {
Blob,
blobFrom,
blobFromSync,
File,
fileFrom,
fileFromSync,
FormData,
Headers,
Request,
Response,
} from 'node-fetch'
if (!globalThis.fetch) {
globalThis.fetch = fetch
globalThis.Headers = Headers
globalThis.Request = Request
globalThis.Response = Response
}
// index.js
import './fetch-polyfill'
// ...Using an old version of node-fetch? Check out the following files:
NOTE: The documentation below is up-to-date with 3.x releases, if you are using an older version, please check how to upgrade.
import fetch from 'node-fetch';
const response = await fetch('https://github.com/');
const body = await response.text();
console.log(body);import fetch from 'node-fetch';
const response = await fetch('https://api.github.com/users/github');
const data = await response.json();
console.log(data);import fetch from 'node-fetch';
const response = await fetch('https://httpbin.org/post', {method: 'POST', body: 'a=1'});
const data = await response.json();
console.log(data);import fetch from 'node-fetch';
const body = {a: 1};
const response = await fetch('https://httpbin.org/post', {
method: 'post',
body: JSON.stringify(body),
headers: {'Content-Type': 'application/json'}
});
const data = await response.json();
console.log(data);URLSearchParams is available on the global object in Node.js as of v10.0.0. See official documentation for more usage methods.
NOTE: The Content-Type header is only set automatically to x-www-form-urlencoded when an instance of URLSearchParams is given as such:
import fetch from 'node-fetch';
const params = new URLSearchParams();
params.append('a', 1);
const response = await fetch('https://httpbin.org/post', {method: 'POST', body: params});
const data = await response.json();
console.log(data);NOTE: 3xx-5xx responses are NOT exceptions, and should be handled in then(), see the next section.
Wrapping the fetch function into a try/catch block will catch all exceptions, such as errors originating from node core libraries, like network errors, and operational errors which are instances of FetchError. See the error handling document for more details.
import fetch from 'node-fetch';
try {
await fetch('https://domain.invalid/');
} catch (error) {
console.log(error);
}It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:
import fetch from 'node-fetch';
class HTTPResponseError extends Error {
constructor(response) {
super(`HTTP Error Response: ${response.status} ${response.statusText}`);
this.response = response;
}
}
const checkStatus = response => {
if (response.ok) {
// response.status >= 200 && response.status < 300
return response;
} else {
throw new HTTPResponseError(response);
}
}
const response = await fetch('https://httpbin.org/status/400');
try {
checkStatus(response);
} catch (error) {
console.error(error);
const errorBody = await error.response.text();
console.error(`Error body: ${errorBody}`);
}Cookies are not stored by default. However, cookies can be extracted and passed by manipulating request and response headers. See Extract Set-Cookie Header for details.
The "Node.js way" is to use streams when possible. You can pipe res.body to another stream. This example uses stream.pipeline to attach stream error handlers and wait for the download to complete.
import {createWriteStream} from 'node:fs';
import {pipeline} from 'node:stream';
import {promisify} from 'node:util'
import fetch from 'node-fetch';
const streamPipeline = promisify(pipeline);
const response = await fetch('https://github.githubassets.com/images/modules/logos_page/Octocat.png');
if (!response.ok) throw new Error(`unexpected response ${response.statusText}`);
await streamPipeline(response.body, createWriteStream('./octocat.png'));In Node.js 14 you can also use async iterators to read body; however, be careful to catch
errors -- the longer a response runs, the more likely it is to encounter an error.
import fetch from 'node-fetch';
const response = await fetch('https://httpbin.org/stream/3');
try {
for await (const chunk of response.body) {
console.dir(JSON.parse(chunk.toString()));
}
} catch (err) {
console.error(err.stack);
}In Node.js 12 you can also use async iterators to read body; however, async iterators with streams
did not mature until Node.js 14, so you need to do some extra work to ensure you handle errors
directly from the stream and wait on it response to fully close.
import fetch from 'node-fetch';
const read = async body => {
let error;
body.on('error', err => {
error = err;
});
for await (const chunk of body) {
console.dir(JSON.parse(chunk.toString()));
}
return new Promise((resolve, reject) => {
body.on('close', () => {
error ? reject(error) : resolve();
});
});
};
try {
const response = await fetch('https://httpbin.org/stream/3');
await read(response.body);
} catch (err) {
console.error(err.stack);
}import fetch from 'node-fetch';
const response = await fetch('https://github.com/');
console.log(response.ok);
console.log(response.status);
console.log(response.statusText);
console.log(response.headers.raw());
console.log(response.headers.get('content-type'));Unlike browsers, you can access raw Set-Cookie headers manually using Headers.raw(). This is a node-fetch only API.
import fetch from 'node-fetch';
const response = await fetch('https://example.com');
// Returns an array of values, instead of a string of comma-separated values
console.log(response.headers.raw()['set-cookie']);import fetch, {
Blob,
blobFrom,
blobFromSync,
File,
fileFrom,
fileFromSync,
} from 'node-fetch'
const mimetype = 'text/plain'
const blob = fileFromSync('./input.txt', mimetype)
const url = 'https://httpbin.org/post'
const response = await fetch(url, { method: 'POST', body: blob })
const data = await response.json()
console.log(data)node-fetch comes with a spec-compliant FormData implementations for posting multipart/form-data payloads
import fetch, { FormData, File, fileFrom } from 'node-fetch'
const httpbin = 'https://httpbin.org/post'
const formData = new FormData()
const binary = new Uint8Array([ 97, 98, 99 ])
const abc = new File([binary], 'abc.txt', { type: 'text/plain' })
formData.set('greeting', 'Hello, world!')
formData.set('file-upload', abc, 'new name.txt')
const response = await fetch(httpbin, { method: 'POST', body: formData })
const data = await response.json()
console.log(data)If you for some reason need to post a stream coming from any arbitrary place, then you can append a Blob or a File look-a-like item.
The minimum requirement is that it has:
- A
Symbol.toStringTaggetter or property that is eitherBloborFile - A known size.
- And either a
stream()method or aarrayBuffer()method that returns a ArrayBuffer.
The stream() must return any async iterable object as long as it yields Uint8Array (or Buffer)
so Node.Readable streams and whatwg streams works just fine.
formData.append('upload', {
[Symbol.toStringTag]: 'Blob',
size: 3,
*stream() {
yield new Uint8Array([97, 98, 99])
},
arrayBuffer() {
return new Uint8Array([97, 98, 99]).buffer
}
}, 'abc.txt')You may cancel requests with AbortController. A suggested implementation is abort-controller.
An example of timing out a request after 150ms could be achieved as the following:
import fetch, { AbortError } from 'node-fetch';
// AbortController was added in node v14.17.0 globally
const AbortController = globalThis.AbortController || await import('abort-controller')
const controller = new AbortController();
const timeout = setTimeout(() => {
controller.abort();
}, 150);
try {
const response = await fetch('https://example.com', {signal: controller.signal});
const data = await response.json();
} catch (error) {
if (error instanceof AbortError) {
console.log('request was aborted');
}
} finally {
clearTimeout(timeout);
}See test cases for more examples.
urlA string representing the URL for fetchingoptionsOptions for the HTTP(S) request- Returns:
Promise<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.
The default values are shown after each option key.
{
// 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`.
}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.
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 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 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, this is useful during a redirection chain across HTTP and HTTPS protocol.
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;
}
}
};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:
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:
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);Passed through to the insecureHTTPParser option on http(s).request. See http.request for more information.
The redirect: 'manual' option for node-fetch is different from the browser & specification, which
results in an opaque-redirect filtered response.
node-fetch gives you the typical basic filtered response instead.
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);
}An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the Body interface.
Due to the nature of Node.js, the following properties are not implemented at this moment:
typedestinationmodecredentialscacheintegritykeepalive
The following node-fetch extension properties are provided:
followcompresscounteragenthighWaterMark
See options for exact meaning of these extensions.
(spec-compliant)
inputA string representing a URL, or anotherRequest(which will be cloned)optionsOptions for the HTTP(S) request
Constructs a new Request object. The constructor is identical to that in the browser.
In most cases, directly fetch(url, options) is simpler than creating a Request object.
An HTTP(S) response. This class implements the Body interface.
The following properties are not implemented in node-fetch at this moment:
trailer
(spec-compliant)
bodyAStringorReadablestreamoptionsAResponseInitoptions dictionary
Constructs a new Response object. The constructor is identical to that in the browser.
Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a Response directly.
(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.
(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.
(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.
This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the Fetch Standard are implemented.
(spec-compliant)
initOptional argument to pre-fill theHeadersobject
Construct a new Headers object. init can be either null, a Headers object, an key-value map object or any iterable object.
// 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);Body is an abstract interface with methods that are applicable to both Request and Response classes.
(deviation from spec)
- Node.js
Readablestream
Data are encapsulated in the Body object. Note that while the Fetch Standard requires the property to always be a WHATWG ReadableStream, in node-fetch it is a Node.js Readable stream.
(spec-compliant)
Boolean
A boolean property for if this body has been consumed. Per the specs, a consumed body cannot be used again.
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.
Code example
import http from 'node:http'
import { Response } from 'node-fetch'
http.createServer(async function (req, res) {
const formData = await new Response(req, {
headers: req.headers // Pass along the boundary value
}).formData()
const allFields = [...formData]
const file = formData.get('uploaded-files')
const arrayBuffer = await file.arrayBuffer()
const text = await file.text()
const whatwgReadableStream = file.stream()
// other was to consume the request could be to do:
const json = await new Response(req).json()
const text = await new Response(req).text()
const arrayBuffer = await new Response(req).arrayBuffer()
const blob = await new Response(req, {
headers: req.headers // So that `type` inherits `Content-Type`
}.blob()
})(node-fetch extension)
An operational error in the fetching process. See ERROR-HANDLING.md for more info.
(node-fetch extension)
An Error thrown when the request is aborted in response to an AbortSignal's abort event. It has a name property of AbortError. See ERROR-HANDLING.MD for more info.
Since 3.x types are bundled with node-fetch, so you don't need to install any additional packages.
For older versions please use the type definitions from DefinitelyTyped:
npm install --save-dev @types/[email protected]Thanks to github/fetch for providing a solid implementation reference.
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|---|---|---|---|---|
| David Frank | Jimmy Wärting | Antoni Kepinski | Richie Bendall | Gregor Martynus |
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