file-type

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.

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Install

npm install file-type

Usage

Node.js

Determine file type from a file:

import {fileTypeFromFile} from 'file-type';

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

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

import {fileTypeFromBuffer} from 'file-type';
import {readChunk} from 'read-chunk';

const buffer = await readChunk('Unicorn.png', {length: 4100});

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

Determine file type from a stream:

import fs from 'node:fs';
import {fileTypeFromStream} from 'file-type';

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

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

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

import got from 'got';
import {fileTypeFromStream} from 'file-type';

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

const stream = got.stream(url);

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

Another stream example:

import stream from 'node:stream';
import fs from 'node:fs';
import crypto from 'node:crypto';
import {fileTypeStream} from 'file-type';

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

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

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

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

Browser

import {fileTypeFromStream} from 'file-type';

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

const response = await fetch(url);
const fileType = await fileTypeFromStream(response.body);

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

import {fileTypeFromBlob} from 'file-type';

const blob = new Blob(['<?xml version="1.0" encoding="ISO-8859-1" ?>'], {
	type: 'plain/text',
	endings: 'native'
});

console.log(await fileTypeFromBlob(blob));
//=> {ext: 'txt', mime: 'plain/text'}

API

fileTypeFromBuffer(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.

fileTypeFromFile(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.

fileTypeFromStream(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.

fileTypeFromTokenizer(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.

import {makeTokenizer} from '@tokenizer/http';
import {fileTypeFromTokenizer} from 'file-type';

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';

const httpTokenizer = await makeTokenizer(audioTrackUrl);
const fileType = await fileTypeFromTokenizer(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:

import S3 from 'aws-sdk/clients/s3';
import {makeTokenizer} from '@tokenizer/s3';
import {fileTypeFromTokenizer} from 'file-type';

// 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 fileTypeFromTokenizer(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).

tokenizer

Type: ITokenizer

A file source implementing the tokenizer interface.

fileTypeStream(readableStream, options?)

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.fromFile().

This method can be handy to put in between a stream, but it comes with a price. Internally stream() builds up a buffer of sampleSize bytes, used as a sample, to determine the file type. The sample size impacts the file detection resolution. A smaller sample size will result in lower probability of the best file type detection.

Note: This method is only available when using Node.js. Note: Requires Node.js 14 or later.

readableStream

Type: stream.Readable

options

Type: object

sampleSize

Type: number
Default: 4100

The sample size in bytes.

Example

import got from 'got';
import {fileTypeStream} from 'file-type';

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

const stream1 = got.stream(url);
const stream2 = await fileTypeStream(stream1, {sampleSize: 1024});

if (stream2.fileType && stream2.fileType.mime === 'image/jpeg') {
	// stream2 can be used to stream the JPEG image (from the very beginning of the stream)
}

readableStream

Type: stream.Readable

The input stream.

supportedExtensions

Returns a Set<string> of supported file extensions.

supportedMimeTypes

Returns a Set<string> of supported MIME types.

Supported file types

• jpg - Joint Photographic Experts Group image
• png - Portable Network Graphics
• apng - Animated Portable Network Graphics
• gif - Graphics Interchange Format
• webp - Web Picture format
• flif - Free Lossless Image Format
• xcf - eXperimental Computing Facility
• 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 - Tagged Image file
• bmp - Bitmap image file
• icns - Apple Icon image
• jxr - Joint Photographic Experts Group extended range
• psd - Adobe Photoshop document
• indd - Adobe InDesign document
• zip - Archive file
• tar - Tarball archive file
• rar - Archive file
• gz - Archive file
• bz2 - Archive file
• zst - Archive file
• 7z - 7-Zip archive
• dmg - Apple Disk Image
• mp4 - MPEG-4 Part 14 video file
• mid - Musical Instrument Digital Interface file
• mkv - Matroska video file
• webm - Web video file
• mov - QuickTime video file
• avi - Audio Video Interleave file
• mpg - MPEG-1 file
• mp1 - MPEG-1 Audio Layer I
• mp2 - MPEG-1 Audio Layer II
• mp3 - Audio file
• ogg - Audio file
• ogv - Audio file
• ogm - Audio file
• oga - Audio file
• spx - Audio file
• ogx - Audio file
• opus - Audio file
• flac - Free Lossless Audio Codec
• wav - Waveform Audio file
• qcp - Tagged and chunked data
• amr - Adaptive Multi-Rate audio codec
• pdf - Portable Document Format
• epub - E-book file
• mobi - Mobipocket
• exe - Executable file
• swf - Adobe Flash Player file
• rtf - Rich Text Format
• woff - Web Open Font Format
• woff2 - Web Open Font Format
• eot - Embedded OpenType font
• ttf - TrueType font
• otf - OpenType font
• ico - Windows icon file
• flv - Flash video
• ps - Postscript
• xz - Compressed file
• sqlite - SQLite file
• nes - Nintendo NES ROM
• crx - Google Chrome extension
• xpi - XPInstall file
• cab - Cabinet file
• deb - Debian package
• ar - Archive file
• rpm - Red Hat Package Manager file
• Z - Unix Compressed File
• lz - Arhive file
• cfb - Compount File Binary Format
• mxf - Material Exchange Format
• mts - MPEG-2 Transport Stream, both raw and Blu-ray Disc Audio-Video (BDAV) versions
• wasm - WebAssembly intermediate compiled format
• blend - Blender project
• bpg - Better Portable Graphics file
• docx - Microsoft Word
• pptx - Microsoft Powerpoint
• xlsx - Microsoft Excel
• jp2 - JPEG 2000
• jpm - JPEG 2000
• jpx - JPEG 2000
• mj2 - Motion JPEG 2000
• aif - Audio Interchange file
• odt - OpenDocument for word processing
• ods - OpenDocument for spreadsheets
• odp - OpenDocument for presentations
• xml - eXtensible Markup Language
• heic - High Efficiency Image File Format
• cur - Icon file
• ktx - OpenGL and OpenGL ES textures
• ape - Monkey's Audio
• wv - WavPack
• asf - Advanced Systems Format
• dcm - DICOM Image File
• mpc - Musepack (SV7 & SV8)
• ics - iCalendar
• vcf - vCard
• 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)
• chm - Microsoft Compiled HTML Help
• 3mf - 3D Manufacturing Format
• jxl - JPEG XL image format

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.

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Related

• file-type-cli - CLI for this module

Maintainers

• Sindre Sorhus
• Mikael Finstad
• Ben Brook
• Borewit