nodejs/doc/api/url.md

URL

Stability: 2 - Stable

The url module provides utilities for URL resolution and parsing. It can be accessed using:

const url = require('url');

URL Strings and URL Objects

A URL string is a structured string containing multiple meaningful components. When parsed, a URL object is returned containing properties for each of these components.

The following details each of the components of a parsed URL. The example 'http://user:pass@host.com:8080/p/a/t/h?query=string#hash' is used to illustrate each.

┌─────────────────────────────────────────────────────────────────────────────┐
│                                    href                                     │
├──────────┬┬───────────┬─────────────────┬───────────────────────────┬───────┤
│ protocol ││   auth    │      host       │           path            │ hash  │
│          ││           ├──────────┬──────┼──────────┬────────────────┤       │
│          ││           │ hostname │ port │ pathname │     search     │       │
│          ││           │          │      │          ├─┬──────────────┤       │
│          ││           │          │      │          │ │    query     │       │
"  http:   // user:pass @ host.com : 8080   /p/a/t/h  ?  query=string   #hash "
│          ││           │          │      │          │ │              │       │
└──────────┴┴───────────┴──────────┴──────┴──────────┴─┴──────────────┴───────┘
(all spaces in the "" line should be ignored -- they are purely for formatting)

urlObject.href

The href property is the full URL string that was parsed with both the protocol and host components converted to lower-case.

For example: 'http://user:pass@host.com:8080/p/a/t/h?query=string#hash'

urlObject.protocol

The protocol property identifies the URL's lower-cased protocol scheme.

For example: 'http:'

urlObject.slashes

The slashes property is a boolean with a value of true if two ASCII forward-slash characters (/) are required following the colon in the protocol.

urlObject.host

The host property is the full lower-cased host portion of the URL, including the port if specified.

For example: 'host.com:8080'

urlObject.auth

The auth property is the username and password portion of the URL, also referred to as "userinfo". This string subset follows the protocol and double slashes (if present) and precedes the host component, delimited by an ASCII "at sign" (@). The format of the string is {username}[:{password}], with the [:{password}] portion being optional.

For example: 'user:pass'

urlObject.hostname

The hostname property is the lower-cased host name portion of the host component without the port included.

For example: 'host.com'

urlObject.port

The port property is the numeric port portion of the host component.

For example: '8080'

urlObject.pathname

The pathname property consists of the entire path section of the URL. This is everything following the host (including the port) and before the start of the query or hash components, delimited by either the ASCII question mark (?) or hash (#) characters.

For example '/p/a/t/h'

No decoding of the path string is performed.

urlObject.search

The search property consists of the entire "query string" portion of the URL, including the leading ASCII question mark (?) character.

For example: '?query=string'

No decoding of the query string is performed.

urlObject.path

The path property is a concatenation of the pathname and search components.

For example: '/p/a/t/h?query=string'

No decoding of the path is performed.

urlObject.query

The query property is either the query string without the leading ASCII question mark (?), or an object returned by the querystring module's parse() method. Whether the query property is a string or object is determined by the parseQueryString argument passed to url.parse().

For example: 'query=string' or {'query': 'string'}

If returned as a string, no decoding of the query string is performed. If returned as an object, both keys and values are decoded.

urlObject.hash

The hash property consists of the "fragment" portion of the URL including the leading ASCII hash (#) character.

For example: '#hash'

url.format(urlObject)

• urlObject {Object | String} A URL object (as returned by url.parse() or constructed otherwise). If a string, it is converted to an object by passing it to url.parse().

The url.format() method returns a formatted URL string derived from urlObject.

If urlObject is not an object or a string, url.parse() will throw a TypeError.

The formatting process operates as follows:

• A new empty string result is created.
• If urlObject.protocol is a string, it is appended as-is to result.
• Otherwise, if urlObject.protocol is not undefined and is not a string, an Error is thrown.
• For all string values of urlObject.protocol that do not end with an ASCII colon (:) character, the literal string : will be appended to result.
• If either of the following conditions is true, then the literal string // will be appended to result:
  • urlObject.slashes property is true;
  • urlObject.protocol begins with http, https, ftp, gopher, or file;
• If the value of the urlObject.auth property is truthy, and either urlObject.host or urlObject.hostname are not undefined, the value of urlObject.auth will be coerced into a string and appended to result followed by the literal string @.
• If the urlObject.host property is undefined then:
  • If the urlObject.hostname is a string, it is appended to result.
  • Otherwise, if urlObject.hostname is not undefined and is not a string, an Error is thrown.
  • If the urlObject.port property value is truthy, and urlObject.hostname is not undefined:
    • The literal string : is appended to result, and
    • The value of urlObject.port is coerced to a string and appended to result.
• Otherwise, if the urlObject.host property value is truthy, the value of urlObject.host is coerced to a string and appended to result.
• If the urlObject.pathname property is a string that is not an empty string:
  • If the urlObject.pathname does not start with an ASCII forward slash (/), then the literal string '/' is appended to result.
  • The value of urlObject.pathname is appended to result.
• Otherwise, if urlObject.pathname is not undefined and is not a string, an Error is thrown.
• If the urlObject.search property is undefined and if the urlObject.query property is an Object, the literal string ? is appended to result followed by the output of calling the querystring module's stringify() method passing the value of urlObject.query.
• Otherwise, if urlObject.search is a string:
  • If the value of urlObject.search does not start with the ASCII question mark (?) character, the literal string ? is appended to result.
  • The value of urlObject.search is appended to result.
• Otherwise, if urlObject.search is not undefined and is not a string, an Error is thrown.
• If the urlObject.hash property is a string:
  • If the value of urlObject.hash does not start with the ASCII hash (#) character, the literal string # is appended to result.
  • The value of urlObject.hash is appended to result.
• Otherwise, if the urlObject.hash property is not undefined and is not a string, an Error is thrown.
• result is returned.

url.format(URL[, options])

Stability: 1 - Experimental

• URL {URL} A WHATWG URL object
• options {Object}
  • auth {Boolean} true if the serialized URL string should include the username and password, false otherwise. Defaults to true.
  • fragment {Boolean} true if the serialized URL string should include the fragment, false otherwise. Defaults to true.
  • search {Boolean} true if the serialized URL string should include the search query, false otherwise. Defaults to true.
  • unicode (Boolean) true if Unicode characters appearing in the host component of the URL string should be encoded directly as opposed to being Punycode encoded. Defaults to false.

Returns a customizable serialization of a URL String representation of a WHATWG URL object.

The URL object has both a toString() method and href property that return string serializations of the URL. These are not, however, customizable in any way. The url.format(URL[, options]) method allows for basic customization of the output.

For example:

const myURL = new URL('https://a:b@你好你好?abc#foo');

console.log(myURL.href);
  // Prints https://a:b@xn--6qqa088eba/?abc#foo

console.log(myURL.toString());
  // Prints https://a:b@xn--6qqa088eba/?abc#foo

console.log(url.format(myURL, {fragment: false, unicode: true, auth: false}));
  // Prints 'https://你好你好?abc'

Note: This variation of the url.format() method is currently considered to be experimental.

url.parse(urlString[, parseQueryString[, slashesDenoteHost]])

• urlString {String} The URL string to parse.
• parseQueryString {Boolean} If true, the query property will always be set to an object returned by the querystring module's parse() method. If false, the query property on the returned URL object will be an unparsed, undecoded string. Defaults to false.
• slashesDenoteHost {Boolean} If true, the first token after the literal string // and preceding the next / will be interpreted as the host. For instance, given //foo/bar, the result would be {host: 'foo', pathname: '/bar'} rather than {pathname: '//foo/bar'}. Defaults to false.

The url.parse() method takes a URL string, parses it, and returns a URL object.

url.resolve(from, to)

• from {String} The Base URL being resolved against.
• to {String} The HREF URL being resolved.

The url.resolve() method resolves a target URL relative to a base URL in a manner similar to that of a Web browser resolving an anchor tag HREF.

For example:

url.resolve('/one/two/three', 'four')         // '/one/two/four'
url.resolve('http://example.com/', '/one')    // 'http://example.com/one'
url.resolve('http://example.com/one', '/two') // 'http://example.com/two'

Escaped Characters

URLs are only permitted to contain a certain range of characters. Spaces (' ') and the following characters will be automatically escaped in the properties of URL objects:

< > " ` \r \n \t { } | \ ^ '

For example, the ASCII space character (' ') is encoded as %20. The ASCII forward slash (/) character is encoded as %3C.

The WHATWG URL API

Stability: 1 - Experimental

The url module provides an experimental implementation of the WHATWG URL Standard as an alternative to the existing url.parse() API.

const URL = require('url').URL;
const myURL = new URL('https://example.org/foo');

console.log(myURL.href);     // https://example.org/foo
console.log(myURL.protocol); // https:
console.log(myURL.hostname); // example.org
console.log(myURL.pathname); // /foo

Note: Using the delete keyword (e.g. delete myURL.protocol, delete myURL.pathname, etc) has no effect but will still return true.

Class: URL

Constructor: new URL(input[, base])

• input {String} The input URL to parse
• base {String | URL} The base URL to resolve against if the input is not absolute.

Creates a new URL object by parsing the input relative to the base. If base is passed as a string, it will be parsed equivalent to new URL(base).

const myURL = new URL('/foo', 'https://example.org/');
  // https://example.org/foo

A TypeError will be thrown if the input or base are not valid URLs. Note that an effort will be made to coerce the given values into strings. For instance:

const myURL = new URL({toString: () => 'https://example.org/'});
  // https://example.org/

Unicode characters appearing within the hostname of input will be automatically converted to ASCII using the Punycode algorithm.

const myURL = new URL('https://你好你好');
  // https://xn--6qqa088eba

Additional examples of parsed URLs may be found in the WHATWG URL Standard.

url.hash

Gets and sets the fragment portion of the URL.

const myURL = new URL('https://example.org/foo#bar');
console.log(myURL.hash);
  // Prints #bar

myURL.hash = 'baz';
console.log(myURL.href);
  // Prints https://example.org/foo#baz

Invalid URL characters included in the value assigned to the hash property are percent-encoded. Note that the selection of which characters to percent-encode may vary somewhat from what the url.parse() and url.format() methods would produce.

url.host

Gets and sets the host portion of the URL.

const myURL = new URL('https://example.org:81/foo');
console.log(myURL.host);
  // Prints example.org:81

myURL.host = 'example.com:82';
console.log(myURL.href);
  // Prints https://example.com:82/foo

Invalid host values assigned to the host property are ignored.

url.hostname

Gets and sets the hostname portion of the URL. The key difference between url.host and url.hostname is that url.hostname does not include the port.

const myURL = new URL('https://example.org:81/foo');
console.log(myURL.hostname);
  // Prints example.org

myURL.hostname = 'example.com:82';
console.log(myURL.href);
  // Prints https://example.com:81/foo

Invalid hostname values assigned to the hostname property are ignored.

url.href

Gets and sets the serialized URL.

const myURL = new URL('https://example.org/foo');
console.log(myURL.href);
  // Prints https://example.org/foo

myURL.href = 'https://example.com/bar'
  // Prints https://example.com/bar

Setting the value of the href property to a new value is equivalent to creating a new URL object using new URL(value). Each of the URL object's properties will be modified.

If the value assigned to the href property is not a valid URL, a TypeError will be thrown.

url.origin

Gets the read-only serialization of the URL's origin. Unicode characters that may be contained within the hostname will be encoded as-is without Punycode encoding.

const myURL = new URL('https://example.org/foo/bar?baz');
console.log(myURL.origin);
  // Prints https://example.org

const idnURL = new URL('https://你好你好');
console.log(idnURL.origin);
  // Prints https://你好你好

console.log(idnURL.hostname);
  // Prints xn--6qqa088eba

url.password

Gets and sets the password portion of the URL.

const myURL = new URL('https://abc:xyz@example.com');
console.log(myURL.password);
  // Prints xyz

myURL.password = '123';
console.log(myURL.href);
  // Prints https://abc:123@example.com

Invalid URL characters included in the value assigned to the password property are percent-encoded. Note that the selection of which characters to percent-encode may vary somewhat from what the url.parse() and url.format() methods would produce.

url.pathname

Gets and sets the path portion of the URL.

const myURL = new URL('https://example.org/abc/xyz?123');
console.log(myURL.pathname);
  // Prints /abc/xyz

myURL.pathname = '/abcdef';
console.log(myURL.href);
  // Prints https://example.org/abcdef?123

Invalid URL characters included in the value assigned to the pathname property are percent-encoded. Note that the selection of which characters to percent-encode may vary somewhat from what the url.parse() and url.format() methods would produce.

url.port

Gets and sets the port portion of the URL. When getting the port, the value is returned as a String.

const myURL = new URL('https://example.org:8888');
console.log(myURL.port);
  // Prints 8888

myURL.port = 1234;
console.log(myURL.href);
  // Prints https://example.org:1234

The port value may be set as either a number or as a String containing a number in the range 0 to 65535 (inclusive). Setting the value to the default port of the URL objects given protocol will result in the port value becoming the empty string ('').

Invalid URL port values assigned to the port property are ignored.

url.protocol

Gets and sets the protocol portion of the URL.

const myURL = new URL('https://example.org');
console.log(myURL.protocol);
  // Prints http:

myURL.protocol = 'ftp';
console.log(myURL.href);
  // Prints ftp://example.org

Invalid URL protocol values assigned to the protocol property are ignored.

url.search

Gets and sets the serialized query portion of the URL.

const myURL = new URL('https://example.org/abc?123');
console.log(myURL.search);
  // Prints ?123

myURL.search = 'abc=xyz';
console.log(myURL.href);
  // Prints https://example.org/abc?abc=xyz

Any invalid URL characters appearing in the value assigned the search property will be percent-encoded. Note that the selection of which characters to percent-encode may vary somewhat from what the url.parse() and url.format() methods would produce.

url.searchParams

Gets a URLSearchParams object representing the query parameters of the URL.

url.username

Gets and sets the username portion of the URL.

const myURL = new URL('https://abc:xyz@example.com');
console.log(myURL.username);
  // Prints abc

myURL.username = '123';
console.log(myURL.href);
  // Prints https://123:xyz@example.com

Any invalid URL characters appearing in the value assigned the username property will be percent-encoded. Note that the selection of which characters to percent-encode may vary somewhat from what the url.parse() and url.format() methods would produce.

url.toString()

The toString() method on the URL object returns the serialized URL. The value returned is equivalent to that of url.href.

Class: URLSearchParams

The URLSearchParams object provides read and write access to the query of a URL. The URLSearchParams class can also be used standalone with one of the four following constructors.

const { URL, URLSearchParams } = require('url');

const myURL = new URL('https://example.org/?abc=123');
console.log(myURL.searchParams.get('abc'));
  // Prints 123

myURL.searchParams.append('abc', 'xyz');
console.log(myURL.href);
  // Prints https://example.org/?abc=123&abc=xyz

myURL.searchParams.delete('abc');
myURL.searchParams.set('a', 'b');
console.log(myURL.href);
  // Prints https://example.org/?a=b

const newSearchParams = new URLSearchParams(myURL.searchParams);
// The above is equivalent to
// const newSearchParams = new URLSearchParams(myURL.search);

newSearchParams.append('a', 'c');
console.log(myURL.href);
  // Prints https://example.org/?a=b
console.log(newSearchParams.toString());
  // Prints a=b&a=c

// newSearchParams.toString() is implicitly called
myURL.search = newSearchParams;
console.log(myURL.href);
  // Prints https://example.org/?a=b&a=c
newSearchParams.delete('a');
console.log(myURL.href);
  // Prints https://example.org/?a=b&a=c

Constructor: new URLSearchParams()

Instantiate a new empty URLSearchParams object.

Constructor: new URLSearchParams(string)

• string {String} A query string

Parse the string as a query string, and use it to instantiate a new URLSearchParams object. A leading '?', if present, is ignored.

const { URLSearchParams } = require('url');
let params;

params = new URLSearchParams('user=abc&query=xyz');
console.log(params.get('user'));
  // Prints 'abc'
console.log(params.toString());
  // Prints 'user=abc&query=xyz'

params = new URLSearchParams('?user=abc&query=xyz');
console.log(params.toString());
  // Prints 'user=abc&query=xyz'

Constructor: new URLSearchParams(obj)

• obj {Object} An object representing a collection of key-value pairs

Instantiate a new URLSearchParams object with a query hash map. The key and value of each property of obj are always coerced to strings.

Note: Unlike querystring module, duplicate keys in the form of array values are not allowed. Arrays are stringified using array.toString(), which simply joins all array elements with commas.

const { URLSearchParams } = require('url');
const params = new URLSearchParams({
  user: 'abc',
  query: ['first', 'second']
});
console.log(params.getAll('query'));
  // Prints ['first,second']
console.log(params.toString());
  // Prints 'user=abc&query=first%2Csecond'

Constructor: new URLSearchParams(iterable)

• iterable {Iterable} An iterable object whose elements are key-value pairs

Instantiate a new URLSearchParams object with an iterable map in a way that is similar to Map's constructor. iterable can be an Array or any iterable object. That means iterable can be another URLSearchParams, in which case the constructor will simply create a clone of the provided URLSearchParams. Elements of iterable are key-value pairs, and can themselves be any iterable object.

Duplicate keys are allowed.

const { URLSearchParams } = require('url');
let params;

// Using an array
params = new URLSearchParams([
  ['user', 'abc'],
  ['query', 'first'],
  ['query', 'second']
]);
console.log(params.toString());
  // Prints 'user=abc&query=first&query=second'

// Using a Map object
const map = new Map();
map.set('user', 'abc');
map.set('query', 'xyz');
params = new URLSearchParams(map);
console.log(params.toString());
  // Prints 'user=abc&query=xyz'

// Using a generator function
function* getQueryPairs() {
  yield ['user', 'abc'];
  yield ['query', 'first'];
  yield ['query', 'second'];
}
params = new URLSearchParams(getQueryPairs());
console.log(params.toString());
  // Prints 'user=abc&query=first&query=second'

// Each key-value pair must have exactly two elements
new URLSearchParams([
  ['user', 'abc', 'error']
]);
  // Throws TypeError: Each query pair must be a name/value tuple

urlSearchParams.append(name, value)

• name {String}
• value {String}

Append a new name-value pair to the query string.

urlSearchParams.delete(name)

• name {String}

Remove all name-value pairs whose name is name.

urlSearchParams.entries()

• Returns: {Iterator}

Returns an ES6 Iterator over each of the name-value pairs in the query. Each item of the iterator is a JavaScript Array. The first item of the Array is the name, the second item of the Array is the value.

Alias for urlSearchParams\[\@\@iterator\]().

urlSearchParams.forEach(fn)

• fn {Function} Function invoked for each name-value pair in the query.

Iterates over each name-value pair in the query and invokes the given function.

const URL = require('url').URL;
const myURL = new URL('https://example.org/?a=b&c=d');
myURL.searchParams.forEach((value, name) => {
  console.log(name, value);
});

urlSearchParams.get(name)

• name {String}
• Returns: {String} or null if there is no name-value pair with the given name.

Returns the value of the first name-value pair whose name is name.

urlSearchParams.getAll(name)

• name {String}
• Returns: {Array}

Returns the values of all name-value pairs whose name is name.

urlSearchParams.has(name)

• name {String}
• Returns: {Boolean}

Returns true if there is at least one name-value pair whose name is name.

urlSearchParams.keys()

• Returns: {Iterator}

Returns an ES6 Iterator over the names of each name-value pair.

urlSearchParams.set(name, value)

• name {String}
• value {String}

Remove any existing name-value pairs whose name is name and append a new name-value pair.

urlSearchParams.toString()

• Returns: {String}

Returns the search parameters serialized as a URL-encoded string.

urlSearchParams.values()

• Returns: {Iterator}

Returns an ES6 Iterator over the values of each name-value pair.

urlSearchParams[@@iterator]()

• Returns: {Iterator}

Returns an ES6 Iterator over each of the name-value pairs in the query string. Each item of the iterator is a JavaScript Array. The first item of the Array is the name, the second item of the Array is the value.

Alias for urlSearchParams.entries().

require('url').domainToAscii(domain)

• domain {String}
• Returns: {String}

Returns the Punycode ASCII serialization of the domain.

Note: The require('url').domainToAscii() method is introduced as part of the new URL implementation but is not part of the WHATWG URL standard.

require('url').domainToUnicode(domain)

• domain {String}
• Returns: {String}

Returns the Unicode serialization of the domain.

Note: The require('url').domainToUnicode() API is introduced as part of the the new URL implementation but is not part of the WHATWG URL standard.

Percent-Encoding in the WHATWG URL Standard

URLs are permitted to only contain a certain range of characters. Any character falling outside of that range must be encoded. How such characters are encoded, and which characters to encode depends entirely on where the character is located within the structure of the URL. The WHATWG URL Standard uses a more selective and fine grained approach to selecting encoded characters than that used by the older url.parse() and url.format() methods.

The WHATWG algorithm defines three "encoding sets" that describe ranges of characters that must be percent-encoded:

• The simple encode set includes code points in range U+0000 to U+001F (inclusive) and all code points greater than U+007E.

• The default encode set includes the simple encode set and code points U+0020, U+0022, U+0023, U+003C, U+003E, U+003F, U+0060, U+007B, and U+007D.

• The userinfo encode set includes the default encode set and code points U+002F, U+003A, U+003B, U+003D, U+0040, U+005B, U+005C, U+005D, U+005E, and U+007C.

The simple encode set is used primary for URL fragments and certain specific conditions for the path. The userinfo encode set is used specifically for username and passwords encoded within the URL. The default encode set is used for all other cases.

When non-ASCII characters appear within a hostname, the hostname is encoded using the Punycode algorithm. Note, however, that a hostname may contain both Punycode encoded and percent-encoded characters. For example:

const URL = require('url').URL;
const myURL = new URL('https://%CF%80.com/foo');
console.log(myURL.href);
  // Prints https://xn--1xa.com/foo
console.log(myURL.origin);
  // Prints https://π.com