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MIME Type
application/x-javascript
Web AssetDeprecatedLegacy non-standard JavaScript MIME type still seen in older systems and outdated server configurations.
MIME type reference, HTTP example, browser usage, common mistakes, and related content.
What is the application/x-javascript MIME type?
The MIME type application/x-javascript is used to tell browsers, APIs, and servers how a file or response body should be interpreted.
MIME stands for Multipurpose Internet Mail Extensions, and MIME types are now a standard part of HTTP responses and web content delivery.
When a browser or client receives a response with application/x-javascript, it uses that information to decide how the content should be processed, rendered, downloaded, or executed.
Example
Content-Type: application/x-javascript
HTTP example
HTTP/1.1 200 OK Content-Type: application/x-javascript Content-Length: 1256
Common file extensions
.js
Common use cases
- Legacy web servers
- Older CMS setups
- Outdated JavaScript delivery
Common mistakes
- Using the wrong MIME type for the file being served
- Returning text/plain instead of application/x-javascript
- Forgetting required parameters like charset when relevant
- Using a deprecated MIME type in older server configurations
- Serving assets with a mismatched Content-Type header, causing browser parsing issues
How browsers use it
Browsers use the Content-Type response header to decide how a response should be handled. For example, HTML is rendered as a page, CSS is parsed as styles, JavaScript is executed as script, and images are displayed visually. If the MIME type is incorrect, the browser may refuse to load the file correctly or may treat it as plain text or a download instead.
Deprecated status
This MIME type is considered outdated in many contexts. A better modern alternative is application/javascript.
Browser support
Often still works in browsers for classic scripts, but should be replaced with application/javascript.
Developer note
You may still encounter this in production on older stacks, but it is not the preferred modern MIME type.