The JavaScript string.includes() method

Q: How do I check if a string contains a substring?

Use str.includes("text"), which returns true or false.

Q: Is string includes() case-sensitive?

Yes. "Hello".includes("hello") is false. Lowercase both sides for a case-insensitive check.

Q: What is the difference between includes() and indexOf()?

includes() returns a boolean; indexOf() returns the position (or -1). Use includes() when you only need yes/no.

Q: How do I check the start of a string?

Use str.startsWith("text") — clearer than includes() when position matters.

Method JavaScript All modern browsers Updated June 23, 2026

Quick answer

The includes() method checks whether a string contains another string and returns true or false. "Hello world".includes("world") is true. It's the clear, modern replacement for indexOf(x) !== -1, and it's case-sensitive.

Overview

includes() answers a simple question: does this string contain that text? It returns a boolean, which reads much better than the old str.indexOf("x") !== -1 idiom. Use it for searching — does the input contain an "@", does the URL include "https", is a keyword present in the title.

It's case-sensitive, so "Hello".includes("hello") is false. When case shouldn't matter, lowercase both sides first: str.toLowerCase().includes(term.toLowerCase()). You can also pass a second argument, a position, to start the search from a given index.

If you specifically need the position of the match, use indexOf() instead. And to check only the start or end of a string, the dedicated startsWith() and endsWith() methods are clearer than a general includes(). There's also an array version of includes() for checking membership in a list.

Syntax

const has = str.includes(searchString)
const has = str.includes(searchString, position)

Parameters

The string.includes() method accepts the following parameters.

Parameter	Description
`searchString`	The text to look for. The match is case-sensitive.
`position`	Optional. The index to start searching from. Defaults to `0`.

Example

Live example

<pre id="out" style="font:15px ui-monospace,monospace"></pre>
<script>
  const title = 'Learn JavaScript Fast';

  document.getElementById('out').textContent =
    'has JavaScript? ' + title.includes('JavaScript') + '\n' +
    'has python?     ' + title.toLowerCase().includes('python');
  // has JavaScript? true / has python? false
</script>

Best practices

Prefer includes() over indexOf(x) !== -1 for a readable presence check.
Lowercase both strings first for a case-insensitive search.
Use startsWith() / endsWith() when you only care about the beginning or end.
Need the position, not just yes/no? Use indexOf().

Frequently asked questions

How do I check if a string contains a substring?

Use str.includes("text"), which returns true or false.

Is string includes() case-sensitive?

Yes. "Hello".includes("hello") is false. Lowercase both sides for a case-insensitive check.

What is the difference between includes() and indexOf()?

includes() returns a boolean; indexOf() returns the position (or -1). Use includes() when you only need yes/no.

How do I check the start of a string?

Use str.startsWith("text") — clearer than includes() when position matters.

string.endsWith() string.indexOf()

References