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A comprehensive library for mime-type mapping

Version published
Install size
133 kB

Package description

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




NPM downloads Mime CI

An API for MIME type information.

  • All mime-db types
  • Compact and dependency-free mime's badge
  • Full TS support

[!Note] mime@4 is now latest. If you're upgrading from mime@3, note the following:

  • mime@4 is API-compatible with mime@3, with one two exceptions:
    • Direct imports of mime properties no longer supported
    • mime.define() cannot be called on the default mime object
  • ESM module support is required. ESM Module FAQ.
  • Requires an ES2020 or newer runtime
  • Built-in Typescript types (@types/mime no longer needed)


npm install mime

Quick Start

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

import mime from 'mime';

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

Lite Version mime/lite's badge

mime/lite is a drop-in mime replacement, stripped of unofficial ("prs.*", "x-*", "vnd.*") types:

import mime from 'mime/lite';



Get mime type for the given file 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


Get file 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'


[!Note] New in mime@4

Get all file extensions for the given mime type.

mime.getAllExtensions('image/jpeg'); // ⇨ Set(3) { 'jpeg', 'jpg', 'jpe' }

Custom Mime instances

The default mime objects are immutable. Custom, mutable versions can be created as follows...

new Mime(type map [, type map, ...])

Create a new, custom mime instance. For example, to create a mutable version of the default mime instance:

import { Mime } from 'mime/lite';

import standardTypes from 'mime/types/standard.js';
import otherTypes from 'mime/types/other.js';

const mime = new Mime(standardTypes, otherTypes);

Each argument is passed to the define() method, below. For example new Mime(standardTypes, otherTypes) is synonomous with new Mime().define(standardTypes).define(otherTypes)

mime.define(type map [, force = false])

[!Note] Only available on custom Mime instances

Define MIME type -> extensions.

Attempting to map a type to an already-defined extension will throw unless the force argument is set to true.

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

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

Command Line

Extension -> type

$ mime scripts/jquery.js

Type -> extension

$ mime -r image/jpeg



Last updated on 25 Apr 2024

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