encodeURI

The encodeURI() function encodes a Uniform Resource Identifier (URI) by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters).

Syntax

encodeURI(URI)

Parameters

URI

A complete Uniform Resource Identifier.

Return value

A new string representing the provided string encoded as a Uniform Resource Identifier (URI).

Description

Assumes that the URI is a complete URI, so does not encode reserved characters that have special meaning in the URI.

encodeURI replaces all characters except the following with the appropriate UTF-8 escape sequences:

Type	Includes
Reserved characters	; , / ? : @ & = + $
Unescaped characters	alphabetic, decimal digits, - _ . ! ~ * ' ( )
Number sign	#

Note that encodeURI by itself cannot form proper HTTP GET and POST requests, such as for XMLHTTPRequests, because "&", "+", and "=" are not encoded, which are treated as special characters in GET and POST requests. encodeURIComponent, however, does encode these characters.

Note that an URIError will be thrown if one attempts to encode a surrogate which is not part of a high-low pair, e.g.,

// high-low pair ok
console.log(encodeURI('\uD800\uDFFF'));

// lone high surrogate throws "URIError: malformed URI sequence"
console.log(encodeURI('\uD800'));

// lone low surrogate throws "URIError: malformed URI sequence"
console.log(encodeURI('\uDFFF')); 

Also note that if one wishes to follow the more recent RFC3986 for URLs, which makes square brackets reserved (for IPv6) and thus not encoded when forming something which could be part of a URL (such as a host), the following code snippet may help:

function fixedEncodeURI(str) {
    return encodeURI(str).replace(/%5B/g, '[').replace(/%5D/g, ']');
}

Specifications

Specification	Status	Comment
ECMAScript 3rd Edition (ECMA-262)	Standard	Initial definition.
ECMAScript 5.1 (ECMA-262) The definition of 'encodeURI' in that specification.	Standard
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'encodeURI' in that specification.	Standard
ECMAScript 2017 Draft (ECMA-262) The definition of 'encodeURI' in that specification.	Draft

Browser compatibility

See also

• decodeURI
• encodeURIComponent
• decodeURIComponent