Ky is a tiny and elegant HTTP client based on the browser Fetch API

Ky targets modern browsers and Deno. For older browsers, you will need to transpile and use a fetch polyfill. For Node.js, check out Got. For isomorphic needs (like SSR), check out ky-universal.

1 KB (minified & gzipped), one file, and no dependencies.

Benefits over plain fetch

• Simpler API
• Method shortcuts (ky.post())
• Treats non-2xx status codes as errors
• Retries failed requests
• JSON option
• Timeout support
• URL prefix option
• Instances with custom defaults
• Hooks

Install

$ npm install ky

Download

• Normal
• Minified

CDN

• jsdelivr
• unpkg

Usage

import ky from 'ky';

(async () => {
	const parsed = await ky.post('https://example.com', {json: {foo: true}}).json();

	console.log(parsed);
	//=> `{data: '🦄'}`
})();

With plain fetch, it would be:

(async () => {
	class HTTPError extends Error {}

	const response = await fetch('https://example.com', {
		method: 'POST',
		body: JSON.stringify({foo: true}),
		headers: {
			'content-type': 'application/json'
		}
	});

	if (!response.ok) {
		throw new HTTPError('Fetch error:', response.statusText);
	}

	const parsed = await response.json();

	console.log(parsed);
	//=> `{data: '🦄'}`
})();

If you are using Deno, import Ky from a URL. For example, using a CDN:

import ky from 'https://unpkg.com/ky/index.js';

In environments that do not support import, you can load ky in UMD format. For example, using require():

const ky = require('ky/umd').default;

With the UMD version, it's also easy to use ky without a bundler or module system.

API

ky(input, [options])

The input and options are the same as fetch, with some exceptions:

• The credentials option is same-origin by default, which is the default in the spec too, but not all browsers have caught up yet.
• Adds some more options. See below.

Returns a Response object with Body methods added for convenience. So you can, for example, call ky.get(input).json() directly without having to await the Response first. When called like that, proper Accept header will be set depending on body method used. Unlike the Body methods of window.Fetch; these will throw an HTTPError if the response status is not in the range 200...299.

ky.get(input, [options])

ky.post(input, [options])

ky.put(input, [options])

ky.patch(input, [options])

ky.head(input, [options])

ky.delete(input, [options])

Sets options.method to the method name and makes a request.

options

Type: Object

method

Type: string Default: get

HTTP method used to make the request.

Internally, the standard methods (GET, POST, PUT, PATCH, HEAD and DELETE) are uppercased in order to avoid server errors due to case sensitivity.

json

Type: Object

Shortcut for sending JSON. Use this instead of the body option. Accepts a plain object which will be JSON.stringify()'d and the correct header will be set for you.

searchParams

Type: string Object<string, string|number> URLSearchParams Default: ''

Search parameters to include in the request URL. Setting this will override all existing search parameters in the input URL.

prefixUrl

Type: string URL

When specified, prefixUrl will be prepended to input. The prefix can be any valid URL, either relative or absolute. A trailing slash / is optional, one will be added automatically, if needed, when joining prefixUrl and input. The input argument cannot start with a / when using this option.

Useful when used with ky.extend() to create niche-specific Ky-instances.

import ky from 'ky';

// On https://example.com

(async () => {
	await ky('unicorn', {prefixUrl: '/api'});
	//=> 'https://example.com/api/unicorn'

	await ky('unicorn', {prefixUrl: 'https://cats.com'});
	//=> 'https://cats.com/unicorn'
})();

retry

Type: number Default: 2

Retry failed requests made with one of the below methods that result in a network error or one of the below status codes.

Methods: GET PUT HEAD DELETE OPTIONS TRACE Status codes: 408 413 429 500 502 503 504

It adheres to the Retry-After response header.

timeout

Type: number false Default: 10000

Timeout in milliseconds for getting a response. Can not be greater than 2147483647. If set to false, there will be no timeout.

hooks

Type: Object<string, Function[]> Default: {beforeRequest: []}

Hooks allow modifications during the request lifecycle. Hook functions may be async and are run serially.

hooks.beforeRequest

Type: Function[] Default: []

This hook enables you to modify the request right before it is sent. Ky will make no further changes to the request after this. The hook function receives the normalized options as the first argument. You could, for example, modify options.headers here.

hooks.afterResponse

Type: Function[] Default: []

This hook enables you to read and optionally modify the response. The hook function receives a clone of the response as the first argument. The return value of the hook function will be used by Ky as the response object if it's an instance of Response.

ky.get('https://example.com', {
	hooks: {
		afterResponse: [
			response => {
				// You could do something with the response, for example, logging.
				log(response);

				// Or return a `Response` instance to overwrite the response.
				return new Response('A different response', {status: 200});
			}
		]
	}
});

throwHttpErrors

Type: boolean Default: true

Throw a HTTPError for error responses (non-2xx status codes).

Setting this to false may be useful if you are checking for resource availability and are expecting error responses.

ky.extend(defaultOptions)

Create a new ky instance with some defaults overridden with your own.

In contrast to ky.create(), ky.extend() inherits defaults from its parent.

ky.create(defaultOptions)

Create a new Ky instance with complete new defaults.

import ky from 'ky';

// On https://my-site.com

const api = ky.create({prefixUrl: 'https://example.com/api'});

(async () => {
	await api.get('users/123');
	//=> 'https://example.com/api/users/123'

	await api.get('/status', {prefixUrl: ''});
	//=> 'https://my-site.com/status'
})();

defaultOptions

Type: Object

ky.HTTPError

Exposed for instanceof checks. The error has a response property with the Response object.

ky.TimeoutError

The error thrown when the request times out.

Tips

Sending Form Data

Sending form data in Ky is identical to fetch. Just pass a FormData instance to the body option. The Content-Type header will be automatically set to multipart/form-data. Setting it manually will result in an error.

// `multipart/form-data`
const formData = new FormData();
formData.append('food', 'fries');
formData.append('drink', 'icetea');

ky.post(url, {
	body: formData
});

If you want to send the data in application/x-www-form-urlencoded format, you will need to encode the data with URLSearchParams.

// `application/x-www-form-urlencoded`
const searchParams = new URLSearchParams();
searchParams.set('food', 'fries');
searchParams.set('drink', 'icetea');

ky.post(url, {
	body: searchParams
});

Cancellation

Fetch (and hence Ky) has built-in support for request cancellation through the AbortController API. Read more.

Example:

import ky from 'ky';

const controller = new AbortController();
const {signal} = controller;

setTimeout(() => controller.abort(), 5000);

(async () => {
	try {
		console.log(await ky(url, {signal}).text());
	} catch (error) {
		if (error.name === 'AbortError') {
			console.log('Fetch aborted');
		} else {
			console.error('Fetch error:', error);
		}
	}
})();

FAQ

How do I use this in Node.js?

Check out ky-universal.

How do I use this with a web app (React, Vue.js, etc.) that uses server-side rendering (SSR)?

Check out ky-universal.

How do I test a browser library that uses this?

Either use a test runner that can run in the browser, like Mocha, or use AVA with ky-universal. Read more.

How do I use this without a bundler like Webpack?

Upload the index.js file in this repo somewhere, for example, to your website server, or use a CDN version. Then import the file.

<script type="module">
// Replace the version number with the latest version
import ky from 'https://cdn.jsdelivr.net/npm/[email protected]/index.js';

(async () => {
	const parsed = await ky('https://jsonplaceholder.typicode.com/todos/1').json();

	console.log(parsed.title);
	//=> 'delectus aut autem
})();
</script>

Alternatively, you can use the umd.js file with a traditional <script> tag (without type="module"), in which case ky will be a global.

<!-- Replace the version number with the latest version -->
<script src="https://cdn.jsdelivr.net/npm/[email protected]/umd.js"></script>
<script>
(async () => {
	const ky = ky.default;
	const parsed = await ky('https://jsonplaceholder.typicode.com/todos/1').json();

	console.log(parsed.title);
	//=> 'delectus aut autem
})();
</script>

How is it different from got

See my answer here. Got is maintained by the same people as Ky.

How is it different from axios?

See my answer here.

How is it different from r2?

See my answer in #10.

What does ky mean?

It's just a random short npm package name I managed to get. It does, however, have a meaning in Japanese:

A form of text-able slang, KY is an abbreviation for 空気読めない (kuuki yomenai), which literally translates into “cannot read the air.” It's a phrase applied to someone who misses the implied meaning.

Browser support

The latest version of Chrome, Firefox, and Safari.

Node.js support

Ky requires Node.js 10 or later, but it indicates Node.js 8 in package.json so you can use it with Node.js 8 by polyfilling the globals without having Yarn fail on install. However, you should just use ky-universal.

Related

• ky-universal - Use Ky in both Node.js and browsers
• got - Simplified HTTP requests for Node.js

Maintainers

• Sindre Sorhus
• Szymon Marczak
• Seth Holladay

License

MIT