The includes() method determines whether one string may be found within another string, returning true or false as appropriate.


str.includes(searchString[, position])


A string to be searched for within str.
position Optional
The position within the string at which to begin searching for searchString. (Defaults to 0.)

Return value

true if the search string is found anywhere within the given string; otherwise, false if not.


This method lets you determine whether or not a string includes another string.


The includes() method is case sensitive. For example, the following expression returns false:

'Blue Whale'.includes('blue')  // returns false


Using includes()

const str = 'To be, or not to be, that is the question.' 

console.log(str.includes('To be'))        // true
console.log(str.includes('question'))     // true
console.log(str.includes('nonexistent'))  // false
console.log(str.includes('To be', 1))     // false
console.log(str.includes('TO BE'))        // false
console.log(str.includes(''))             // true


This method has been added to the ECMAScript 2015 specification and may not be available in all JavaScript implementations yet.

However, you can easily polyfill this method:

if (!String.prototype.includes) {
  String.prototype.includes = function(search, start) {
    'use strict';

    if (search instanceof RegExp) {
      throw TypeError('first argument must not be a RegExp');
    if (start === undefined) { start = 0; }
    return this.indexOf(search, start) !== -1;


ECMAScript (ECMA-262)
The definition of 'String.prototype.includes' in that specification.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
includesChrome Full support 41Edge Full support 12Firefox Full support 40
Full support 40
No support 18 — 48
Alternate Name
Alternate Name Uses the non-standard name: contains
IE No support NoOpera Full support 28Safari Full support 9WebView Android Full support 41Chrome Android Full support 41Firefox Android Full support 40
Full support 40
No support 18 — 48
Alternate Name
Alternate Name Uses the non-standard name: contains
Opera Android Full support 28Safari iOS Full support 9Samsung Internet Android Full support 4.0nodejs Full support 4.0.0


Full support  
Full support
No support  
No support
Uses a non-standard name.
Uses a non-standard name.


In Firefox 18–39, the name of this method was contains(). It was renamed to includes() in bug 1102219 due to the following reason:

It's been reported that some websites using MooTools 1.2 broke on Firefox 17. This version of MooTools checks whether String.prototype.contains() exists and, if it doesn't,  MooTools adds its own function.

With the introduction of this function in Firefox 17, the behavior of that check changed in a way that causes code based on MooTools' String.prototype.contains() implementation to break. As a result, the implementation was disabled in Firefox 17 and String.prototype.contains() was available one version later, in Firefox 18, when outreach to MooTools was leading to the release of MooTools version 1.2.6.

MooTools 1.3 forces its own version of String.prototype.contains(), so websites relying on it should not break. However, you should note that MooTools 1.3 signature and ECMAScript 2015 signatures for this method differ (on the second argument). Later, MooTools 1.5+ changed the signature to match the ES2015 standard.

In Firefox 48, String.prototype.contains() has been removed. Use String.prototype.includes() only.

See also