file-type

Detect the file type of a Buffer/Uint8Array

The file type is detected by checking the magic number of the buffer.

Install

$ npm install --save file-type

Usage

Node.js

var readChunk = require('read-chunk'); // npm install read-chunk
var fileType = require('file-type');
var buffer = readChunk.sync('unicorn.png', 0, 262);

fileType(buffer);
//=> {ext: 'png', mime: 'image/png'}

or from a remote location:

var http = require('http');
var fileType = require('file-type');
var url = 'http://assets-cdn.github.com/images/spinners/octocat-spinner-32.gif';

http.get(url, function (res) {
	res.once('data', function (chunk) {
		res.destroy();
		console.log(fileType(chunk));
		//=> {ext: 'gif', mime: 'image/gif'}
	});
});

Browser

var xhr = new XMLHttpRequest();
xhr.open('GET', 'unicorn.png');
xhr.responseType = 'arraybuffer';

xhr.onload = function () {
	fileType(new Uint8Array(this.response));
	//=> {ext: 'png', mime: 'image/png'}
};

xhr.send();

API

fileType(buffer)

Returns an object (or null when no match) with:

• ext - one of the supported file types
• mime - the MIME type

buffer

Type: buffer (Node.js), uint8array

It only needs the first 262 bytes.

CLI

$ npm install --global file-type

$ file-type --help

  Usage
    file-type <filename>
    cat <filename> | file-type

  Example
    cat unicorn.png | file-type
    png

Supported file types

• jpg
• png
• gif
• webp
• tif
• bmp
• jxr
• psd
• zip
• tar
• rar
• gz
• bz2
• 7z
• mp4
• mkv
• webm
• mov
• avi
• mpg
• mp3
• m4a
• ogg
• flac
• wav
• pdf
• epub
• exe
• swf
• rtf

SVG isn't included as it requires the whole file to be read, but you can get it here.

PR welcome for additional commonly used file types.

License

MIT © Sindre Sorhus