---
title: "detectContentType"
source: "https://github.com/remix-run/remix/blob/8905f3943706e1f53696ab83e70a84873cabfc90/packages/mime/src/lib/detect-content-type.ts#L20"
---

# detectContentType

## Summary

Detects the Content-Type header value for a given file extension or filename.

Returns a full Content-Type value including charset when appropriate, based on
the charset defined in mime-db for the detected MIME type.

## Signature

```ts
function detectContentType(extension: string): string | undefined

```

## Example

```ts
detectContentType('css') // 'text/css;charset=utf-8'
detectContentType('.css') // 'text/css;charset=utf-8'
detectContentType('style.css') // 'text/css;charset=utf-8'
detectContentType('image.png') // 'image/png'
detectContentType('unknown') // undefined

```

## Parameters

### `extension`

The file extension (e.g. "css", ".css") or filename (e.g. "style.css")

## Returns

The Content-Type value, or undefined if not found