What is MIME type "application/javascript"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

application/javascript signals that a file holds JavaScript code. It directs browsers and servers to treat the file as a script that adds interactive behavior to web pages.
The MIME type is vital for ensuring that code runs correctly and securely in modern web environments.

Ensures browsers activate the JavaScript engine for dynamic behavior
Supports client-side interactivity on websites
Facilitates integration with server-side templating systems
Standardizes how script files are treated across different platforms

Files that use this MIME type include those with extensions such as JS, ES, SNAP, and JS.ERB.

Associated file extensions

.js, .es, .snap, .js.erb

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: application/javascript

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="application/javascript">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');
    
    http.createServer((req, res) => {
      res.setHeader('Content-Type', 'application/javascript');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.js, .es, .snap, .js.erb

FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.