Detect the file type of a Buffer/Uint8Array/ArrayBuffer

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

$ npm install file-type

const readChunk = require('read-chunk');
const fileType = require('file-type');

const buffer = readChunk.sync('unicorn.png', 0, fileType.minimumBytes);

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

Or from a remote location:

const http = require('http');
const fileType = require('file-type');

const url = 'https://assets-cdn.github.com/images/spinners/octocat-spinner-32.gif';

http.get(url, response => {
	response.on('readable', () => {
		const chunk = response.read(fileType.minimumBytes);
		response.destroy();

		console.log(fileType(chunk));
		//=> {ext: 'gif', mime: 'image/gif'}
	});
});

Or from a stream:

const stream = require('stream');
const fs = require('fs');
const crypto = require('crypto');
const fileType = require('file-type');

(async () => {
	const read = fs.createReadStream('encrypted.enc');
	const decipher = crypto.createDecipheriv(alg, key, iv);

	const fileTypeStream = await fileType.stream(stream.pipeline(read, decipher));

	console.log(fileTypeStream.fileType);
	//=> {ext: 'mov', mime: 'video/quicktime'}

	const write = fs.createWriteStream(`decrypted.${fileTypeStream.fileType.ext}`);
	fileTypeStream.pipe(write);
})();

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

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

xhr.send();

Returns an object with:

• ext - One of the supported file types
• mime - The MIME type

Or undefined when there is no match.

Type: Buffer | Uint8Array | ArrayBuffer

It only needs the first .minimumBytes bytes. The exception is detection of docx, pptx, and xlsx which potentially requires reading the whole file.

Type: number

The minimum amount of bytes needed to detect a file type. Currently, it's 4100 bytes, but it can change, so don't hardcode it.

Detect the file type of a readable stream.

Returns a Promise which resolves to the original readable stream argument, but with an added fileType property, which is an object like the one returned from fileType().

Note: This method is only for Node.js.

Type: stream.Readable

Returns a set of supported file extensions.

Returns a set of supported MIME types.

• jpg
• png
• apng - Animated Portable Network Graphics
• gif
• webp
• flif
• cr2 - Canon Raw image file (v2)
• orf - Olympus Raw image file
• arw - Sony Alpha Raw image file
• dng - Adobe Digital Negative image file
• nef - Nikon Electronic Format image file
• rw2 - Panasonic RAW image file
• raf - Fujifilm RAW image file
• tif
• bmp
• jxr
• psd
• zip
• tar
• rar
• gz
• bz2
• 7z
• dmg
• mp4
• mid
• mkv
• webm
• mov
• avi
• mpg
• mp2
• mp3
• ogg
• ogv
• ogm
• oga
• spx
• ogx
• opus
• flac
• wav
• qcp
• amr
• pdf
• epub
• mobi - Mobipocket
• exe
• swf
• rtf
• woff
• woff2
• eot
• ttf
• otf
• ico
• flv
• ps
• xz
• sqlite
• nes
• crx
• xpi
• cab
• deb
• ar
• rpm
• Z
• lz
• msi
• mxf
• mts
• wasm
• blend
• bpg
• docx
• pptx
• xlsx
• jp2 - JPEG 2000
• jpm - JPEG 2000
• jpx - JPEG 2000
• mj2 - Motion JPEG 2000
• aif
• odt - OpenDocument for word processing
• ods - OpenDocument for spreadsheets
• odp - OpenDocument for presentations
• xml
• heic
• cur
• ktx
• ape - Monkey's Audio
• wv - WavPack
• asf - Advanced Systems Format
• wma - Windows Media Audio
• wmv - Windows Media Video
• dcm - DICOM Image File
• mpc - Musepack (SV7 & SV8)
• ics - iCalendar
• glb - GL Transmission Format
• pcap - Libpcap File Format
• dsf - Sony DSD Stream File (DSF)
• lnk - Microsoft Windows file shortcut
• alias - macOS Alias file
• voc - Creative Voice File
• ac3 - ATSC A/52 Audio File
• 3gp - Multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services
• 3g2 - Multimedia container format defined by the 3GPP2 for 3G CDMA2000 multimedia services
• m4v - MPEG-4 Visual bitstreams
• m4p - MPEG-4 files with audio streams encrypted by FairPlay Digital Rights Management as were sold through the iTunes Store
• m4a - Audio-only MPEG-4 files
• m4b - Audiobook and podcast MPEG-4 files, which also contain metadata including chapter markers, images, and hyperlinks
• f4v - ISO base media file format used by Adobe Flash Player
• f4p - ISO base media file format protected by Adobe Access DRM used by Adobe Flash Player
• f4a - Audio-only ISO base media file format used by Adobe Flash Player
• f4b - Audiobook and podcast ISO base media file format used by Adobe Flash Player
• mie - Dedicated meta information format which supports storage of binary as well as textual meta information
• shp - Geospatial vector data format
• arrow - Columnar format for tables of data

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

Pull requests are welcome for additional commonly used file types, except for doc, xls, ppt.

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• file-type-cli - CLI for this module

• Sindre Sorhus
• Mikael Finstad
• Ben Brook