URL: URL() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨April 2021⁩.

Note: This feature is available in Web Workers.

The URL() constructor returns a newly created URL object representing the URL defined by the parameters.

If the given base URL or the resulting URL are not valid URLs, the JavaScript TypeError exception is thrown.

A string or any other object with a stringifier that represents an absolute URL or a relative reference to a base URL. If url is a relative reference, base is required, and is used to resolve the final URL. If url is an absolute URL, a given base will not be used to create the resulting URL.

base Optional

A string representing the base URL to use in cases where url is a relative reference. If not specified, it defaults to undefined.

When a base is specified, the resolved URL is not simply a concatenation of url and base. Relative references to the parent and current directory are resolved relative to the current directory of the base URL, which includes path segments up until the last forward-slash, but not any after. Relative references to the root are resolved relative to the base origin. For more information see Resolving relative references to a URL.

Note: The url and base arguments will each be stringified from whatever value you pass, such as an HTMLAnchorElement or HTMLAreaElement element, just like with other Web APIs that accept a string. In particular, you can use an existing URL object for either argument, and it will be stringified from the object's href property.

Exceptions

TypeError: url (in the case of absolute URLs) or base + url (in the case of relative references) is not a valid URL.

Examples

Here are some examples of using the constructor.

Note: Resolving relative references to a URL provides additional examples demonstrating how different url and base values are resolved to a final absolute URL.

// Base URLs:
let baseUrl = "https://developer.mozilla.org";

let a = new URL("/", baseUrl);
// => 'https://developer.mozilla.org/'

let b = new URL(baseUrl);
// => 'https://developer.mozilla.org/'

new URL("en-US/docs", b);
// => 'https://developer.mozilla.org/en-US/docs'

let d = new URL("/en-US/docs", b);
// => 'https://developer.mozilla.org/en-US/docs'

new URL("/en-US/docs", d);
// => 'https://developer.mozilla.org/en-US/docs'

new URL("/en-US/docs", a);
// => 'https://developer.mozilla.org/en-US/docs'

new URL("/en-US/docs", "https://developer.mozilla.org/fr-FR/toto");
// => 'https://developer.mozilla.org/en-US/docs'

Here are some examples of invalid URLs:

new URL("/en-US/docs", "");
// Raises a TypeError exception as '' is not a valid URL

new URL("/en-US/docs");
// Raises a TypeError exception as '/en-US/docs' is not a valid URL

// Other cases:

new URL("http://www.example.com");
// => 'http://www.example.com/'

new URL("http://www.example.com", B);
// => 'http://www.example.com/'

new URL("", "https://example.com/?query=1");
// => 'https://example.com/?query=1' (Edge before 79 removes query arguments)

new URL("/a", "https://example.com/?query=1");
// => 'https://example.com/a' (see relative URLs)

new URL("//foo.com", "https://example.com");
// => 'https://foo.com/' (see relative URLs)