readme.md

file-type

Detect the file type of a Buffer/Uint8Array/ArrayBuffer

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

Install

$ npm install file-type

Usage

Node.js

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 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 stream = await fileType.stream(read.pipe(decipher));

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

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

Browser

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();

API

fileType(input)

Returns an Object with:

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

Or null when there is no match.

input

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.

fileType.minimumBytes

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.

fileType.stream(readableStream)

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.

readableStream

Type: stream.Readable

Supported file types

• jpg
• png
• gif
• webp
• flif
• cr2
• tif
• bmp
• jxr
• psd
• zip
• tar
• rar
• gz
• bz2
• 7z
• dmg
• mp4
• m4v
• mid
• mkv
• webm
• mov
• avi
• wmv
• mpg
• mp2
• mp3
• m4a
• ogg
• 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
• 3gp
• 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)

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

Pull request welcome for additional commonly used file types.

Related

• file-type-cli - CLI for this module

Created by

• Sindre Sorhus
• Mikael Finstad

License

MIT