mime-types

Unlike the older mime@1.x module, mime-types does not provide fallbacks. If a lookup fails or the input is invalid, the functions return false. To provide a default value, use a logical OR operator:

var type = mime.lookup('unrecognized') || 'application/octet-stream';

Install the mime-types module using the npm registry:

$ npm install mime-types

Use mime.lookup(path) to retrieve the MIME content-type associated with a file extension or a file path. Returns false if the type is not found.

mime.lookup('json') // 'application/json'
mime.lookup('.md') // 'text/markdown'
mime.lookup('file.html') // 'text/html'
mime.lookup('folder/file.js') // 'text/javascript'
mime.lookup('folder/.htaccess') // false

mime.lookup('cats') // false

Use mime.charset(type) to look up the implied default charset for a specific content-type.

mime.charset('text/markdown') // 'UTF-8'

Use mime.extension(type) to retrieve the default file extension for a given MIME content-type. Returns false if not found.

mime.extension('application/octet-stream') // 'bin'

Use mime.contentType(type) to generate a full Content-Type header.

• If passed an extension, it uses mime.lookup to find the content-type.
• If passed a content-type, it uses that directly.
• If the resulting content-type lacks a charset parameter, it automatically appends the default charset retrieved via mime.charset.

Note: If the input already contains a charset, it is preserved.

mime.contentType('markdown') // 'text/x-markdown; charset=utf-8'
mime.contentType('file.json') // 'application/json; charset=utf-8'
mime.contentType('text/html') // 'text/html; charset=utf-8'
mime.contentType('text/html; charset=iso-8859-1') // 'text/html; charset=iso-8859-1'

// from a full path
mime.contentType(path.extname('/path/to/file.json')) // 'application/json; charset=utf-8'

The module provides two direct mapping objects for quick lookups:

• mime.types: A map where keys are extensions and values are content-types.
• mime.extensions: A map where keys are content-types and values are arrays of associated extensions.

Use charset(type) to retrieve the default character set for a specific MIME type.

• For types with a defined charset in the database, it returns that charset.
• For text/* types without a specific charset defined, it defaults to 'UTF-8'.
• If no charset can be determined, it returns false.

Use contentType(str) to generate a full Content-Type header string. The input str can be either a MIME type (e.g., text/html) or a file extension (e.g., html).

If a MIME type is provided, the function automatically appends the default charset (e.g., ; charset=utf-8) if one is available for that type. If an extension is provided, it first performs a lookup to find the MIME type and then applies the charset logic.

The module exports two internal maps that can be used for direct lookups:

• types: A map where keys are extensions (without the dot) and values are the preferred MIME types.
• extensions: A map where keys are MIME types and values are arrays of associated extensions.