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When encoding a query string to be sent to a web server - when do you use escape() and when do you use encodeURI() or encodeURIComponent():

Use escape:

escape("% +&=");

OR

use encodeURI() / encodeURIComponent()

encodeURI(";var2=value2");

encodeURIComponent("var1=value1&var2=value2");

When encoding a query string to be sent to a web server - when do you use escape() and when do you use encodeURI() or encodeURIComponent():

Use escape:

escape("% +&=");

OR

use encodeURI() / encodeURIComponent()

encodeURI("http://www.google.com?var1=value1&var2=value2");

encodeURIComponent("var1=value1&var2=value2");
Share Improve this question edited Jul 31, 2023 at 8:27 Penny Liu 17.3k5 gold badges86 silver badges108 bronze badges asked Sep 16, 2008 at 19:24 AdamAdam 28.8k15 gold badges61 silver badges73 bronze badges 6
  • 138 It's worth pointing out that encodeURIComponent("var1=value1&var2=value2") is not the typical use case. That example will encode the = and &, which is probably not what was intended! encodeURIComponent is typically applied separately to just the value in each key value pair (the part after each =). – Timothy Shields Commented Mar 14, 2014 at 20:45
  • 3 do you need to do anything to the key? What if it has an = in it? (is that even possible?) – Mala Commented Jun 9, 2014 at 21:49
  • 3 @Mala I'm still new to web programming in general, but what I've used in my limited experience is to encode the key and the value separately, ensuring the '=' stays: var params = encodeURIComponent(key) + '=' + encodeURIComponent(value); - Maybe someone else knows a better way. – Ned Commented Jun 28, 2014 at 21:17
  • 1 @nedshares I was playing with that, but as far as I can tell the key doesn't seem to be encoded... at least not in the same way. Maybe it's against spec to have an = in the key? – Mala Commented Jul 1, 2014 at 20:08
  • 3 Also worth pointing out that recent JavaScript implementations provide the higher-level interfaces URL and URLSearchParams for manipulating URLs and their query strings. – Bart Robinson Commented Dec 6, 2017 at 0:07
 |  Show 1 more comment

16 Answers 16

Reset to default 2020

escape()

Don't use it! escape() is defined in section B.2.1.1 escape and the introduction text of Annex B says:

... All of the language features and behaviours specified in this annex have one or more undesirable characteristics and in the absence of legacy usage would be removed from this specification. ...
... Programmers should not use or assume the existence of these features and behaviours when writing new ECMAScript code....

Behaviour:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/escape

Special characters are encoded with the exception of: @*_+-./

The hexadecimal form for characters, whose code unit value is 0xFF or less, is a two-digit escape sequence: %xx.

For characters with a greater code unit, the four-digit format %uxxxx is used. This is not allowed within a query string (as defined in RFC3986):

query       = *( pchar / "/" / "?" )
pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
pct-encoded   = "%" HEXDIG HEXDIG
sub-delims    = "!" / "$" / "&" / "'" / "(" / ")"
              / "*" / "+" / "," / ";" / "="

A percent sign is only allowed if it is directly followed by two hexdigits, percent followed by u is not allowed.

encodeURI()

Use encodeURI when you want a working URL. Make this call:

encodeURI("http://www.example.org/a file with spaces.html")

to get:

http://www.example.org/a%20file%20with%20spaces.html

Don't call encodeURIComponent since it would destroy the URL and return

http%3A%2F%2Fwww.example.org%2Fa%20file%20with%20spaces.html

Note that encodeURI, like encodeURIComponent, does not escape the ' character.

encodeURIComponent()

Use encodeURIComponent when you want to encode the value of a URL parameter.

var p1 = encodeURIComponent("http://example.org/?a=12&b=55")

Then you may create the URL you need:

var url = "http://example.net/?param1=" + p1 + "&param2=99";

And you will get this complete URL:

http://example.net/?param1=http%3A%2F%2Fexample.org%2F%Ffa%3D12%26b%3D55&param2=99

Note that encodeURIComponent does not escape the ' character. A common bug is to use it to create html attributes such as href='MyUrl', which could suffer an injection bug. If you are constructing html from strings, either use " instead of ' for attribute quotes, or add an extra layer of encoding (' can be encoded as %27).

For more information on this type of encoding you can check: http://en.wikipedia.org/wiki/Percent-encoding

The difference between encodeURI() and encodeURIComponent() are exactly 11 characters encoded by encodeURIComponent but not by encodeURI:

I generated this table easily with console.table in Google Chrome with this code:

var arr = [];
for(var i=0;i<256;i++) {
  var char=String.fromCharCode(i);
  if(encodeURI(char)!==encodeURIComponent(char)) {
    arr.push({
      character:char,
      encodeURI:encodeURI(char),
      encodeURIComponent:encodeURIComponent(char)
    });
  }
}
console.table(arr);

I found this article enlightening : Javascript Madness: Query String Parsing

I found it when I was trying to undersand why decodeURIComponent was not decoding '+' correctly. Here is an extract:

String:                         "A + B"
Expected Query String Encoding: "A+%2B+B"
escape("A + B") =               "A%20+%20B"     Wrong!
encodeURI("A + B") =            "A%20+%20B"     Wrong!
encodeURIComponent("A + B") =   "A%20%2B%20B"   Acceptable, but strange

Encoded String:                 "A+%2B+B"
Expected Decoding:              "A + B"
unescape("A+%2B+B") =           "A+++B"       Wrong!
decodeURI("A+%2B+B") =          "A+++B"       Wrong!
decodeURIComponent("A+%2B+B") = "A+++B"       Wrong!

encodeURIComponent doesn't encode -_.!~*'(), causing problem in posting data to php in xml string.

For example:
<xml><text x="100" y="150" value="It's a value with single quote" /> </xml>

General escape with encodeURI
%3Cxml%3E%3Ctext%20x=%22100%22%20y=%22150%22%20value=%22It's%20a%20value%20with%20single%20quote%22%20/%3E%20%3C/xml%3E

You can see, single quote is not encoded. To resolve issue I created two functions to solve issue in my project, for Encoding URL:

function encodeData(s:String):String{
    return encodeURIComponent(s).replace(/\-/g, "%2D").replace(/\_/g, "%5F").replace(/\./g, "%2E").replace(/\!/g, "%21").replace(/\~/g, "%7E").replace(/\*/g, "%2A").replace(/\'/g, "%27").replace(/\(/g, "%28").replace(/\)/g, "%29");
}

For Decoding URL:

function decodeData(s:String):String{
    try{
        return decodeURIComponent(s.replace(/\%2D/g, "-").replace(/\%5F/g, "_").replace(/\%2E/g, ".").replace(/\%21/g, "!").replace(/\%7E/g, "~").replace(/\%2A/g, "*").replace(/\%27/g, "'").replace(/\%28/g, "(").replace(/\%29/g, ")"));
    }catch (e:Error) {
    }
    return "";
}

encodeURI() - the escape() function is for javascript escaping, not HTTP.

Small comparison table Java vs. JavaScript vs. PHP.

1. Java URLEncoder.encode (using UTF8 charset)
2. JavaScript encodeURIComponent
3. JavaScript escape
4. PHP urlencode
5. PHP rawurlencode

char   JAVA JavaScript --PHP---
[ ]     +    %20  %20  +    %20
[!]     %21  !    %21  %21  %21
[*]     *    *    *    %2A  %2A
[']     %27  '    %27  %27  %27 
[(]     %28  (    %28  %28  %28
[)]     %29  )    %29  %29  %29
[;]     %3B  %3B  %3B  %3B  %3B
[:]     %3A  %3A  %3A  %3A  %3A
[@]     %40  %40  @    %40  %40
[&]     %26  %26  %26  %26  %26
[=]     %3D  %3D  %3D  %3D  %3D
[+]     %2B  %2B  +    %2B  %2B
[$]     %24  %24  %24  %24  %24
[,]     %2C  %2C  %2C  %2C  %2C
[/]     %2F  %2F  /    %2F  %2F
[?]     %3F  %3F  %3F  %3F  %3F
[#]     %23  %23  %23  %23  %23
[[]     %5B  %5B  %5B  %5B  %5B
[]]     %5D  %5D  %5D  %5D  %5D
----------------------------------------
[~]     %7E  ~    %7E  %7E  ~
[-]     -    -    -    -    -
[_]     _    _    _    _    _
[%]     %25  %25  %25  %25  %25
[\]     %5C  %5C  %5C  %5C  %5C
----------------------------------------
char  -JAVA-  --JavaScript--  -----PHP------
[ä]   %C3%A4  %C3%A4  %E4     %C3%A4  %C3%A4
[ф]   %D1%84  %D1%84  %u0444  %D1%84  %D1%84

I recommend not to use one of those methods as is. Write your own function which does the right thing.

MDN has given a good example on url encoding shown below.

var fileName = 'my file(2).txt';
var header = "Content-Disposition: attachment; filename*=UTF-8''" + encodeRFC5987ValueChars(fileName);

console.log(header); 
// logs "Content-Disposition: attachment; filename*=UTF-8''my%20file%282%29.txt"


function encodeRFC5987ValueChars (str) {
    return encodeURIComponent(str).
        // Note that although RFC3986 reserves "!", RFC5987 does not,
        // so we do not need to escape it
        replace(/['()]/g, escape). // i.e., %27 %28 %29
        replace(/\*/g, '%2A').
            // The following are not required for percent-encoding per RFC5987, 
            //  so we can allow for a little better readability over the wire: |`^
            replace(/%(?:7C|60|5E)/g, unescape);
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent

For the purpose of encoding javascript has given three inbuilt functions -

  1. escape() - does not encode @*/+ This method is deprecated after the ECMA 3 so it should be avoided.

  2. encodeURI() - does not encode ~!@#$&*()=:/,;?+' It assumes that the URI is a complete URI, so does not encode reserved characters that have special meaning in the URI. This method is used when the intent is to convert the complete URL instead of some special segment of URL. Example - encodeURI('http://stackoverflow.com'); will give - http://stackoverflow.com

  3. encodeURIComponent() - does not encode - _ . ! ~ * ' ( ) This function encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character. This method should be used to convert a component of URL. For instance some user input needs to be appended Example - encodeURIComponent('http://stackoverflow.com'); will give - http%3A%2F%2Fstackoverflow.com

All this encoding is performed in UTF 8 i.e the characters will be converted in UTF-8 format.

encodeURIComponent differ from encodeURI in that it encode reserved characters and Number sign # of encodeURI

Also remember that they all encode different sets of characters, and select the one you need appropriately. encodeURI() encodes fewer characters than encodeURIComponent(), which encodes fewer (and also different, to dannyp's point) characters than escape().

Inspired by Johann's table, I've decided to extend the table. I wanted to see which ASCII characters get encoded.

var ascii = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";

var encoded = [];

ascii.split("").forEach(function (char) {
    var obj = { char };
    if (char != encodeURI(char))
        obj.encodeURI = encodeURI(char);
    if (char != encodeURIComponent(char))
        obj.encodeURIComponent = encodeURIComponent(char);
    if (obj.encodeURI || obj.encodeURIComponent)
        encoded.push(obj);
});

console.table(encoded);

Table shows only the encoded characters. Empty cells mean that the original and the encoded characters are the same.


Just to be extra, I'm adding another table for urlencode() vs rawurlencode(). The only difference seems to be the encoding of space character.

<script>
<?php
$ascii = str_split(" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~", 1);
$encoded = [];
foreach ($ascii as $char) {
    $obj = ["char" => $char];
    if ($char != urlencode($char))
        $obj["urlencode"] = urlencode($char);
    if ($char != rawurlencode($char))
        $obj["rawurlencode"] = rawurlencode($char);
    if (isset($obj["rawurlencode"]) || isset($obj["rawurlencode"]))
        $encoded[] = $obj;
}
echo "var encoded = " . json_encode($encoded) . ";";
?>
console.table(encoded);
</script>

Just try encodeURI() and encodeURIComponent() yourself...

console.log(encodeURIComponent('@#$%^&*'));

Input: @#$%^&*. Output: %40%23%24%25%5E%26*. So, wait, what happened to *? Why wasn't this converted? It could definitely cause problems if you tried to do linux command "$string". TLDR: You actually want fixedEncodeURIComponent() and fixedEncodeURI(). Long-story...

When to use encodeURI()? Never. encodeURI() fails to adhere to RFC3986 with regard to bracket-encoding. Use fixedEncodeURI(), as defined and further explained at the MDN encodeURI() Documentation...

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

When to use encodeURIComponent()? Never. encodeURIComponent() fails to adhere to RFC3986 with regard to encoding: !'()*. Use fixedEncodeURIComponent(), as defined and further explained at the MDN encodeURIComponent() Documentation...

function fixedEncodeURIComponent(str) {
 return encodeURIComponent(str).replace(/[!'()*]/g, function(c) {
   return '%' + c.charCodeAt(0).toString(16);
 });
}

Then you can use fixedEncodeURI() to encode a single URL piece, whereas fixedEncodeURIComponent() will encode URL pieces and connectors; or, simply, fixedEncodeURI() will not encode +@?=:#;,$& (as & and + are common URL operators), but fixedEncodeURIComponent() will.

I've found that experimenting with the various methods is a good sanity check even after having a good handle of what their various uses and capabilities are.

Towards that end I have found this website extremely useful to confirm my suspicions that I am doing something appropriately. It has also proven useful for decoding an encodeURIComponent'ed string which can be rather challenging to interpret. A great bookmark to have:

http://www.the-art-of-web.com/javascript/escape/

The accepted answer is good. To extend on the last part:

Note that encodeURIComponent does not escape the ' character. A common bug is to use it to create html attributes such as href='MyUrl', which could suffer an injection bug. If you are constructing html from strings, either use " instead of ' for attribute quotes, or add an extra layer of encoding (' can be encoded as %27).

If you want to be on the safe side, percent encoding unreserved characters should be encoded as well.

You can use this method to escape them (source Mozilla)

function fixedEncodeURIComponent(str) {
  return encodeURIComponent(str).replace(/[!'()*]/g, function(c) {
    return '%' + c.charCodeAt(0).toString(16);
  });
}

// fixedEncodeURIComponent("'") --> "%27"

Modern rewrite of @johann-echavarria's answer:

console.log(
    Array(256)
        .fill()
        .map((ignore, i) => String.fromCharCode(i))
        .filter(
            (char) =>
                encodeURI(char) !== encodeURIComponent(char)
                    ? {
                          character: char,
                          encodeURI: encodeURI(char),
                          encodeURIComponent: encodeURIComponent(char)
                      }
                    : false
        )
)

Or if you can use a table, replace console.log with console.table (for the prettier output).

I have this function...

var escapeURIparam = function(url) {
    if (encodeURIComponent) url = encodeURIComponent(url);
    else if (encodeURI) url = encodeURI(url);
    else url = escape(url);
    url = url.replace(/\+/g, '%2B'); // Force the replacement of "+"
    return url;
};

Short Answer

for data only intended to be parsed by JavaScript, use escape(), for anything else, use encodeURIComponent()

encodeURI and encodeURIComponent

encodeURI and encodeURIComponent do the same thing: they URL-Encode a string. There is an important difference, though: encodeURI respects the structure of an URI, while encodeURIComponent does not. In most cases, you won't notice the difference, but when the argument you pass is a valid URI, encodeURI won't encode some characters of it, while encodeURIComponent ignores the URI structure of the passed argument, and encodes all characters which are invalid/have special meaning in an URI:

console.log(encodeURIComponent("Some Example Text"),encodeURI("Some Example Text"));//==>Some%20Example%20Text Some%20Example%20Text
console.log(encodeURIComponent("https://example.com/äöü?param1=content"),encodeURI("https://example.com/äöü?param1=content"));

In the example above, you can clearly see how encodeURIComponent behaves the same way as encodeURI when no URI structure is given, but when it is given, encodeURI skips characters relevant to the URI's structure, where encodeURIComponent ignores these. In most cases, encodeURIComponent is what you want. I cannot think of any use cases where encodeURI is the better choice, if you have user data, it is better to do:

var url="https://example.com/upload?input="+encodeURIComponent(user_input);

instead of:

var url=encodeURI("https://example.com/upload?input="+user_input)

because a user might insert URI-corrupting data (accidentally or maliciously (even though preventing attacks on client-side is a bad idea anyways) or because a malicious actor told him to) like:

upload_data?second_parameter=unintended_content

which the would be encoded properly in example 1, but generate errorneous or even malicious URI's in example 2.

BOTH METHODS THROW AN ERROR IF A LONE SURROGATE (0xD800-0xDFFFF) IS IN THE PASSED STRING

escape

Even though escape might look like it URI-Encodes a string, it actually translates it into a javascript specific format. When only characters in range (0x00-0x7F) are encoded, it behaves the same as encodeURIComponent (not encodeURI, because it ignores the URI structure just like encodeURIComponent does), except for 3 special characters, which it does not encode, even though they might have a special meaning in the URI (@+/). Behaviour differs for code points above 0x7F:

escape translates it into %uXXXX when the code point is above 0xFF, for code points in range 0x80-0xFF, escape translates it into %XX

encodeURIComponent URL-encodes it regularly, and throws an URIError for lone surrogates, which is the reason why escape() is the more robust method.

//0x00-0x7F
console.log(escape("Some Example Text"),encodeURIComponent("Some Example Text")); //==> Some%20Example%20Text Some%20Example%20Text
//Special Characters
console.log(escape("@+/"),encodeURIComponent("@+/"))//==>@+/ %40%2B%2F
//Above 0x7F
console.log(escape(String.fromCodePoint(0x1234)),encodeURIComponent(String.fromCodePoint(0x1234)));//==> %u1234 %E1%88%B4
//2 Valid Surrogates
console.log(escape("

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