mime

What is mime?

The mime npm package is a utility for handling and transforming file MIME types. It provides functionality to lookup the MIME type for a file based on its extension, determine the default extension for a MIME type, and define custom MIME type mappings.

What are mime's main functionalities?

Lookup MIME type by extension

This feature allows you to get the MIME type for a given file extension. In the code sample, we are looking up the MIME type for a '.json' file, which returns 'application/json'.

const mime = require('mime');
const mimeType = mime.getType('json'); // 'application/json'

Lookup extension by MIME type

This feature enables you to find the default file extension for a given MIME type. In the code sample, we are finding the extension for the MIME type 'application/json', which returns 'json'.

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

Define custom MIME type mappings

This feature allows you to define custom MIME type mappings. In the code sample, we are adding a custom MIME type 'text/x-some-format' with multiple extensions. The second argument 'true' indicates that the custom types should take precedence over the built-in types.

const mime = require('mime');
mime.define({ 'text/x-some-format': ['x-sf', 'x-sft', 'x-sfml'] }, true);

Other packages similar to mime

mime-types

The 'mime-types' package is similar to 'mime' in that it provides MIME type lookup based on file extension and vice versa. It is based on the mime-db dataset, which is a comprehensive dataset of MIME types compiled from various sources. Compared to 'mime', it might offer a more extensive and updated list of MIME types.

file-type

The 'file-type' package goes beyond simple MIME type lookup by extension; it can detect the actual MIME type of a file or a Buffer by checking the file's magic numbers (file signatures). This can be more reliable than 'mime' when dealing with files that have incorrect or missing extensions.

README

Mime

A comprehensive, compact MIME type module.

Version 2 Notes

Version 2 is a breaking change from 1.x, as the semver implies. Specifically:

• ES6 support required (node@>=6)
• lookup() renamed to getType()
• extension() renamed to getExtension()
• charset() and load() methods have been removed

If you prefer the legacy version of this module please npm install mime@^1. Version 1 docs may be found here.

Install - NPM

npm install mime

Quick Start

For the full version (800+ MIME types, 1,000+ extensions):

const mime = require('mime');

mime.getType('txt');                    // ⇨ 'text/plain'
mime.getExtension('text/plain');        // ⇨ 'txt'

See Mime API below for API details.

Lite Version

There is also a "lite" version of this module that omits vendor-specific (*/vnd.*) and experimental (*/x-*) types. It weighs in at ~2.5KB, compared to 8KB for the full version. To load the lite version:

const mime = require('mime/lite');

Browser-ready Versions

To use this module in the browser, you would typlically use webpack or browserify to package your code. However, browser-ready versions are available via wzrd.in. E.g. For the full version:

<script src="http://wzrd.in/standalone/mime@latest"></script>

Or, for the "lite" version:

<script src="http://wzrd.in/standalone/mime%2flite@latest"></script>

Then:

<script>
mime.getType(...); // etc.
</script>

Mime .vs. mime-types .vs. mime-db modules

For those of you wondering about the difference between these [popular] NPM modules, here's a brief rundown ...

mime-db is "the source of truth" for MIME type information. It is not an API. Rather, it is a canonical dataset of mime type definitions pulled from IANA, Apache, NGINX, and custom mappings submitted by the Node.js community.

mime-types is a thin wrapper around mime-db that provides an API drop-in compatible(ish) with mime @ < v1.3.6 API.

mime is, as of v2, a self-contained module bundled with a pre-optimized version of the mime-db dataset. It provides a simplified API with the following characteristics:

• Internally consistent type ⇔ extension mapping. I.e. mime.getType(mime.getExtension(type)) == type will always be true
• Method naming consistent with industry best-practices
• Compact footprint. E.g. The minified+compressed sizes of the various modules:

Module	Size
mime-db	18 KB
mime-types	same as mime-db
mime	8 KB
mime/lite	2 KB

Mime API

Both require('mime') and require('mime/lite') return instances of the MIME class, documented below.

new Mime(typeMap, ... more maps)

Most users of this module will not need to create Mime instances directly. However if you would like to create custom mappings, you may do so as follows ...

// Require Mime class
const Mime = require('mime/Mime');

// Define mime type -> extensions map
const typeMap = {
  'text/abc': ['abc', 'alpha', 'bet'],
  'text/def': ['leppard']
};

// Create and use Mime instance
const myMime = new Mime(typeMap);
myMime.getType('abc');            // ⇨ 'text/abc'
myMime.getExtension('text/def');  // ⇨ 'leppard'

If more than one map argument is provided, each map is define()ed (see below), in order.

mime.getType(pathOrExtension)

Get mime type for the given path or extension. E.g.

mime.getType('js');             // ⇨ 'application/javascript'
mime.getType('json');           // ⇨ 'application/json'

mime.getType('txt');            // ⇨ 'text/plain'
mime.getType('dir/text.txt');   // ⇨ 'text/plain'
mime.getType('dir\\text.txt');  // ⇨ 'text/plain'
mime.getType('.text.txt');      // ⇨ 'text/plain'
mime.getType('.txt');           // ⇨ 'text/plain'

null is returned in cases where an extension is not detected or recognized

mime.getType('foo/txt');        // ⇨ null
mime.getType('bogus_type');     // ⇨ null

mime.getExtension(type)

Get extension for the given mime type. Charset options (often included in Content-Type headers) are ignored.

mime.getExtension('text/plain');               // ⇨ 'txt'
mime.getExtension('application/json');         // ⇨ 'json'
mime.getExtension('text/html; charset=utf8');  // ⇨ 'html'

mime.define(typeMap[, force = false])

Define [more] type mappings.

typeMap is a map of type -> extensions, as documented in new Mime, above.

By default this method will throw an error if you try to map a type to an extension that is already assigned to another type. Passing true for the force argument will suppress this behavior (overriding any previous mapping).

mime.define({'text/x-abc': ['abc', 'abcd']});

mime.getType('abcd');            // ⇨ 'text/x-abc'
mime.getExtension('text/x-abc')  // ⇨ 'abc'

Command Line

mime [path_or_extension]

E.g.

> mime scripts/jquery.js
application/javascript

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