.js MIME type

Q: What is the MIME type for .js files?

text/javascript. You may also see application/javascript, application/x-javascript, but text/javascript is the one to send. The same type covers .mjs, .cjs.

Q: What Content-Type header should a .js file be served with?

Content-Type: text/javascript; charset=utf-8. As a text format, include the charset so browsers don't guess the encoding. It compresses well, so let the server apply gzip or Brotli.

JavaScripttext & code

text/javascript

JavaScript, including ES modules. RFC 9239 made text/javascript the one standard type.

MIME type	text/javascript
Extensions	.js, .mjs, .cjs
Also seen as	application/javascript, application/x-javascript
Content-Type	text/javascript; charset=utf-8
Compress in transit?	Yes — enable gzip or Brotli

Good to know

application/javascript still works everywhere but is obsolete; new configs should use text/javascript.
ES modules (<script type="module">) are blocked unless served with a JavaScript MIME type — make sure your server maps .mjs too.
Under nosniff, a script served as text/plain or application/octet-stream is blocked.

Serve .js files with the right type

The response header to send:

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

Most servers pick the type from the file extension. If yours sends the wrong one, map it explicitly:

nginx (inside the types block in mime.types)

text/javascript js mjs cjs;

Apache (.htaccess or server config)

AddType text/javascript .js .mjs .cjs

Express

res.set("Content-Type", "text/javascript; charset=utf-8");

Python

import mimetypes

mimetypes.add_type("text/javascript", ".js")
mimetypes.add_type("text/javascript", ".mjs")
mimetypes.add_type("text/javascript", ".cjs")

HTML file input

<input type="file" accept=".js,.mjs,.cjs,text/javascript">

Check it

See what a server sends for a file, and what type a local file really is by its contents:

curl -sI https://example.com/file.js | grep -i '^content-type:'
file --mime-type file.js

Frequently asked questions

What is the MIME type for .js files?

text/javascript. You may also see application/javascript, application/x-javascript, but text/javascript is the one to send. The same type covers .mjs, .cjs.

What Content-Type header should a .js file be served with?

Content-Type: text/javascript; charset=utf-8. As a text format, include the charset so browsers don't guess the encoding. It compresses well, so let the server apply gzip or Brotli.

Related types

.json .html .wasm .map all MIME types →

Headers that go with it: Content-Type · Content-Disposition · X-Content-Type-Options