What Is a .js File? .js Format, MIME & How to Open

Quick facts

Extension.js

File typeJavaScript File

MIME typetext/javascript

CategoryData & Text

CharsetUTF-8

CompressibleYes

Format familyjavascript

What is .js

What is a .js file?

A .js file is a JavaScript File — JavaScript source file for web and Node.js applications.

In the mime-db registry it maps to text/javascript with UTF-8 encoding, and it is marked as compressible. When serving .js over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to text/javascript and is used by JavaScript among others — and is delivered over HTTP via the Content-Type header.

How to open .js files

Use VS Code or Node.js to open and edit .js files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: text/javascript; charset=utf-8

Common software that reads/writes .js:

VS CodeNode.jsChrome DevTools

Relation chain

.jsextension of

format

javascriptserved as

mime type

text/javascriptsent via header

http header

Related extensions

Related MIME types

application/javascript

.js

Related programming languages

JavaScript

.js ._js .bones

Common uses

Configuration files
Data interchange between systems
API request and response payloads
Logs and data exports

How to edit .js files

Open the file with VS Code, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .js files

Create a new file and save it with the .js extension, or export this format from VS Code.

Example

function greet(name) {
  return `Hello, ${name}!`;
}

greet('World');

Frequently asked questions

What programs can open .js files?

Common options include VS Code, Node.js, Chrome DevTools. You can also open many of these files with built-in viewers or a browser.

How do I create a .js file?

Create a new file in any text editor or the app that owns the format and save it with the .js extension.

What is the relationship between .js and the text/javascript MIME type?

text/javascript is the media type identifier used for .js files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-08-18

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