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).

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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

Does not encode characters that have special meaning (reserved characters) for a URI. The following example shows all the parts that a URI "scheme" can possibly contain. Note how certain characters are used to signify special meaning:

http://username:password@www.example.com:80/path/to/file.php?foo=316&bar=this+has+spaces#anchor

Hence encodeURI does not encode characters that are necessary to formulate a complete URI. Also, encodeURI does not encode a few additional characters, known as "unreserved marks", which do not have a reserved purpose but are allowed in a URI "as is".  (See RFC2396)

encodeURI escapes all characters except:

Not Escaped:

    A-Z a-z 0-9 ; , / ? : @ & = + $ - _ . ! ~ * ' ( ) #

encodeURI differs from encodeURIComponent as follows:

var set1 = ";,/?:@&=+$#";  // Reserved Characters
var set2 = "-_.!~*'()";   // Unreserved Marks
var set3 = "ABC abc 123"; // Alphanumeric Characters + Space

console.log(encodeURI(set1)); // ;,/?:@&=+$#
console.log(encodeURI(set2)); // -_.!~*'()
console.log(encodeURI(set3)); // ABC%20abc%20123 (the space gets encoded as %20)

console.log(encodeURIComponent(set1)); // %3B%2C%2F%3F%3A%40%26%3D%2B%24%23
console.log(encodeURIComponent(set2)); // -_.!~*'()
console.log(encodeURIComponent(set3)); // ABC%20abc%20123 (the space gets encoded as %20)

Note that a 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(encodeURIComponent('\uD800\uDFFF'));

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

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

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, ']');
}

Alternative URI encoding scheme is Base62x,  which has been ported into NPM.

Specifications

Browser compatibility

See also

• decodeURI
• encodeURIComponent
• decodeURIComponent
• Base62x