mime-types

What is mime-types?

The mime-types npm package is a utility for resolving file extensions to MIME types and vice versa. It is based on the mime-db dataset, which is a comprehensive set of MIME type definitions.

What are mime-types's main functionalities?

Lookup MIME type for a file extension

This feature allows you to find the MIME type for a given file extension. If the extension has a MIME type in the database, it will return it as a string; otherwise, it will return false.

const mime = require('mime-types');
const mimeType = mime.lookup('json'); // 'application/json'

Determine the default extension for a MIME type

This feature enables you to find the default file extension for a given MIME type. If the MIME type has an associated extension, it will return it as a string; otherwise, it will return false.

const mime = require('mime-types');
const extension = mime.extension('application/json'); // 'json'

Lookup charset for a MIME type

This feature allows you to find the default charset for a given MIME type, which can be useful when setting the 'Content-Type' header in HTTP responses.

const mime = require('mime-types');
const charset = mime.charset('text/markdown'); // 'UTF-8'

Content-Type parsing

This feature is used to build a full Content-Type header given a MIME type or extension. It will also append the charset parameter when appropriate.

const mime = require('mime-types');
const contentType = mime.contentType('markdown'); // 'text/markdown; charset=utf-8'

Other packages similar to mime-types

mime

The 'mime' package is similar to 'mime-types' and provides MIME type lookup and extension lookup. It differs in that it allows for custom MIME type definitions and has a slightly different API.

file-type

The 'file-type' package is used to detect the file type and MIME type of a Buffer/Uint8Array/ArrayBuffer. Unlike 'mime-types', it does not rely on file extensions and can detect the type of binary content.

README

mime-types

The ultimate javascript content-type utility.

Similar to the mime@1.x module, except:

• No fallbacks. Instead of naively returning the first available type, mime-types simply returns false, so do var type = mime.lookup('unrecognized') || 'application/octet-stream'.
• No new Mime() business, so you could do var lookup = require('mime-types').lookup.
• No .define() functionality
• Bug fixes for .lookup(path)

Otherwise, the API is compatible with mime 1.x.

Install

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install mime-types

Note on MIME Type Data and Semver

This package considers the programmatic api as the semver compatibility. Additionally, the package which provides the MIME data for this package (mime-db) also considers it's programmatic api as the semver contract. This means the MIME type resolution is not considered in the semver bumps.

In the past the version of mime-db was pinned to give two decision points when adopting MIME data changes. This is no longer true. We still update the mime-db package here as a minor release when necessary, but will use a ^ range going forward. This means that if you want to pin your mime-db data you will need to do it in your application. While this expectation was not set in docs until now, it is how the pacakge operated, so we do not feel this is a breaking change.

If you wish to pin your mime-db version you can do that with overrides via your package manager of choice. See their documentation for how to correctly configure that.

Adding Types

All mime types are based on mime-db, so open a PR there if you'd like to add mime types.

API

var mime = require('mime-types')

All functions return false if input is invalid or not found.

mime.lookup(path)

Lookup the content-type associated with a file.

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

mime.lookup('cats') // false

mime.contentType(type)

Create a full content-type header given a content-type or extension. When given an extension, mime.lookup is used to get the matching content-type, otherwise the given content-type is used. Then if the content-type does not already have a charset parameter, mime.charset is used to get the default charset and add to the returned content-type.

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'

mime.extension(type)

Get the default extension for a content-type.

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

mime.charset(type)

Lookup the implied default charset of a content-type.

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

var type = mime.types[extension]

A map of content-types by extension.

[extensions...] = mime.extensions[type]

A map of extensions by content-type.

License

MIT