filetype.js

Detect the file type of a Buffer/Uint8Array/ArrayBuffer

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

This package is for detecting binary-based file formats, not text-based formats like .txt, .csv, .svg, etc.

Installation

$ npm install @jedithepro/filetype.js

Usage

Node.js

Determine file type from a file:

const FileType = require('@jedithepro/filetype.js');

(async () => {
	console.log(await FileType.fromFile('Unicorn.png'));
	//=> {ext: 'png', mime: 'image/png'}
})();

Determine file type from a Buffer, which may be a portion of the beginning of a file:

const FileType = require('@jedithepro/filetype.js');
const readChunk = require('read-chunk');

(async () => {
	const buffer = readChunk.sync('Unicorn.png', 0, 4100);

	console.log(await FileType.fromBuffer(buffer));
	//=> {ext: 'png', mime: 'image/png'}
})();

Determine file type from a stream:

const fs = require('fs');
const FileType = require('@jedithepro/filetype.js');

(async () => {
	const stream = fs.createReadStream('Unicorn.mp4');

	console.log(await FileType.fromStream(stream));
	//=> {ext: 'mp4', mime: 'video/mp4'}
}
)();

The stream method can also be used to read from a remote location:

const got = require('got');
const FileType = require('@jedithepro/filetype.js');

const url = 'https://upload.wikimedia.org/wikipedia/en/a/a9/Example.jpg';

(async () => {
	const stream = got.stream(url);

	console.log(await FileType.fromStream(stream));
	//=> {ext: 'jpg', mime: 'image/jpeg'}
})();

Another stream example:

const stream = require('stream');
const fs = require('fs');
const crypto = require('crypto');
const FileType = require('@jedithepro/filetype.js');

(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);
})();

API

FileType.fromBuffer(buffer)

Detect the file type of a Buffer, Uint8Array, or ArrayBuffer.

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

If file access is available, it is recommended to use FileType.fromFile() instead.

Returns a Promise for an object with the detected file type and MIME type:

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

Or undefined when there is no match.

buffer

Type: Buffer | Uint8Array | ArrayBuffer

A buffer representing file data. It works best if the buffer contains the entire file, it may work with a smaller portion as well.

FileType.fromFile(filePath)

Detect the file type of a file path.

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

Returns a Promise for an object with the detected file type and MIME type:

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

Or undefined when there is no match.

filePath

Type: string

The file path to parse.

FileType.fromStream(stream)

Detect the file type of a Node.js readable stream.

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

Returns a Promise for an object with the detected file type and MIME type:

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

Or undefined when there is no match.

stream

Type: stream.Readable

A readable stream representing file data.

FileType.fromTokenizer(tokenizer)

Detect the file type from an ITokenizer source.

This method is used internally, but can also be used for a special "tokenizer" reader.

A tokenizer propagates the internal read functions, allowing alternative transport mechanisms, to access files, to be implemented and used.

Returns a Promise for an object with the detected file type and MIME type:

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

Or undefined when there is no match.

An example is @tokenizer/http, which requests data using HTTP-range-requests. A difference with a conventional stream and the tokenizer, is that it can ignore (seek, fast-forward) in the stream. For example, you may only need and read the first 6 bytes, and the last 128 bytes, which may be an advantage in case reading the entire file would take longer.

const {makeTokenizer} = require('@tokenizer/http');
const FileType = require('@jedithepro/filetype.js');

const audioTrackUrl = 'https://test-audio.netlify.com/Various%20Artists%20-%202009%20-%20netBloc%20Vol%2024_%20tiuqottigeloot%20%5BMP3-V2%5D/01%20-%20Diablo%20Swing%20Orchestra%20-%20Heroines.mp3';

(async () => {
	const httpTokenizer = await makeTokenizer(audioTrackUrl);
	const fileType = await FileType.fromTokenizer(httpTokenizer);

	console.log(fileType);
	//=> {ext: 'mp3', mime: 'audio/mpeg'}
})();

Or use @tokenizer/s3 to determine the file type of a file stored on Amazon S3:

const FileType = require('@jedithepro/filetype.js');
const S3 = require('aws-sdk/clients/s3');
const {makeTokenizer} = require('@tokenizer/s3');

(async () => {
	// Initialize the S3 client
	const s3 = new S3();

	// Initialize the S3 tokenizer.
	const s3Tokenizer = await makeTokenizer(s3, {
		Bucket: 'affectlab',
		Key: '1min_35sec.mp4'
	});

	// Figure out what kind of file it is.
	const fileType = await FileType.fromTokenizer(s3Tokenizer);
	console.log(fileType);
})();

Note that only the minimum amount of data required to determine the file type is read (okay, just a bit extra to prevent too many fragmented reads).

FileType.extensions

Returns a set of supported file extensions.

FileType.mimeTypes

Returns a set of supported MIME types.

Supported file types

• jpg
• png
• apng - Animated Portable Network Graphics
• gif
• webp
• flif
• cr2 - Canon Raw image file (v2)
• cr3 - Canon Raw image file (v3)
• 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
• icns
• jxr
• psd
• indd
• zip
• tar
• rar
• gz
• bz2
• 7z
• dmg
• mp4
• mid
• mkv
• webm
• mov
• avi
• mpg
• mp1 - MPEG-1 Audio Layer I
• 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
• cfb
• 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
• 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
• aac - Advanced Audio Coding
• it - Audio module format: Impulse Tracker
• s3m - Audio module format: ScreamTracker 3
• xm - Audio module format: FastTracker 2
• ai - Adobe Illustrator Artwork
• skp - SketchUp
• avif - AV1 Image File Format
• eps - Encapsulated PostScript
• lzh - LZH archive
• pgp - Pretty Good Privacy
• asar - Archive format primarily used to enclose Electron applications
• stl - Standard Tesselated Geometry File Format (ASCII only)

Pull requests are welcome for additional commonly used file types.

The following file types will not be accepted:

• MS-CFB: Microsoft Compound File Binary File Format based formats, too old and difficult to parse:
  • .doc - Microsoft Word 97-2003 Document
  • .xls - Microsoft Excel 97-2003 Document
  • .ppt - Microsoft PowerPoint97-2003 Document
  • .msi - Microsoft Windows Installer
• .csv - Reason.
• .svg - Detecting it requires a full-blown parser. Check out is-svg for something that mostly works.