file type

Detect the file type of a file, stream, or data

3736

356

JavaScript

Detect the file type of a file, stream, or data

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.

We accept contributions for commonly used modern file formats, not historical or obscure ones. Open an issue first for discussion.

Install

npm install file-type

This package is an ESM package. Your project needs to be ESM too. Read more.

If you use it with Webpack, you need the latest Webpack version and ensure you configure it correctly for ESM.

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 Uint8Array/ArrayBuffer, 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'}

API

fileTypeFromBuffer(buffer)

Detect the file type of a 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 fileTypeFromFile() instead.

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

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

Or undefined when there is no match.

buffer

Type: 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.

This is for Node.js only.

To read from a File, see fileTypeFromBlob().

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

Returns a Promise for an object with the detected file 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 web ReadableStream.

If the engine is Node.js, this may also be a Node.js stream.Readable.

Direct support for Node.js streams will be dropped in the future, when Node.js streams can be converted to Web streams (see toWeb()).

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

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

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

Or undefined when there is no match.

stream

Type: Web ReadableStream or Node.js stream.Readable

A readable stream representing file data.

fileTypeFromBlob(blob)

Detect the file type of a Blob,

[!TIP]
A File object is a Blob and can be passed in here.

It will stream the underlying Blob.

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

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

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

Or undefined when there is no match.

import {fileTypeFromBlob} from 'file-type';

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

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

[!WARNING]
This method depends on ReadableStreamBYOBReader which requires Node.js ≥ 20
and may not be available in all modern browsers.

To work around this limitation, you can use an alternative approach to read and process the Blob without relying on streaming:

import {fileTypeFromBuffer} from 'file-type';

async function readFromBlobWithoutStreaming(blob) {
	const buffer = await blob.arrayBuffer();
	return fileTypeFromBuffer(buffer);
}

blob

Type: Blob

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:

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(webStream, 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 fileTypeFromFile().

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: When using Node.js, a stream.Readable may be provided as well.

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?.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.

Custom detectors

A custom detector is a function that allows specifying custom detection mechanisms.

An iterable of detectors can be provided via the fileTypeOptions argument for the FileTypeParser constructor.
In Node.js, you should use NodeFileTypeParser, which extends FileTypeParser and provides access to Node.js specific functions.

The detectors are called before the default detections in the provided order.

Custom detectors can be used to add new FileTypeResults or to modify return behaviour of existing FileTypeResult detections.

If the detector returns undefined, there are 2 possible scenarios:

The detector has not read from the tokenizer, it will be proceeded with the next available detector.
The detector has read from the tokenizer (tokenizer.position has been increased).
In that case no further detectors will be executed and the final conclusion is that file-type returns undefined.
Note that this an exceptional scenario, as the detector takes the opportunity from any other detector to determine the file type.

Example detector array which can be extended and provided to each public method via the fileTypeOptions argument:

import {FileTypeParser} from 'file-type'; // or `NodeFileTypeParser` in Node.js

const customDetectors = [
	async tokenizer => {
		const unicornHeader = [85, 78, 73, 67, 79, 82, 78]; // 'UNICORN' as decimal string

		const buffer = new Uint8Array(7);
		await tokenizer.peekBuffer(buffer, {length: unicornHeader.length, mayBeLess: true});

		if (unicornHeader.every((value, index) => value === buffer[index])) {
			return {ext: 'unicorn', mime: 'application/unicorn'};
		}

		return undefined;
	},
];

const buffer = new Uint8Array(new TextEncoder().encode('UNICORN'));
const parser = new FileTypeParser({customDetectors}); // `NodeFileTypeParser({customDetectors})` in Node.js
const fileType = await parser.fromBuffer(buffer);
console.log(fileType);

Abort signal

Some async operations can be aborted by passing an AbortSignal to the FileTypeParser constructor.

import {FileTypeParser} from 'file-type'; // or `NodeFileTypeParser` in Node.js

const abortController = new AbortController()

const parser = new FileTypeParser({abortSignal: abortController.signal});

const promise = parser.fromStream(blob.stream());

abortController.abort(); // Abort file-type reading from the Blob stream.

Supported file types

3g2 - Multimedia container format defined by the 3GPP2 for 3G CDMA2000 multimedia services
3gp - Multimedia container format defined by the Third Generation Partnership Project (3GPP) for 3G UMTS multimedia services
3mf - 3D Manufacturing Format
7z - 7-Zip archive
Z - Unix Compressed File
aac - Advanced Audio Coding
ac3 - ATSC A/52 Audio File
ace - ACE archive
ai - Adobe Illustrator Artwork
aif - Audio Interchange file
alias - macOS Alias file
amr - Adaptive Multi-Rate audio codec
ape - Monkey’s Audio
apk - Android package format
apng - Animated Portable Network Graphics
ar - Archive file
arj - Archive file
arrow - Columnar format for tables of data
arw - Sony Alpha Raw image file
asar - Archive format primarily used to enclose Electron applications
asf - Advanced Systems Format
avi - Audio Video Interleave file
avif - AV1 Image File Format
avro - Object container file developed by Apache Avro
blend - Blender project
bmp - Bitmap image file
bpg - Better Portable Graphics file
bz2 - Archive file
cab - Cabinet file
cfb - Compound File Binary Format
chm - Microsoft Compiled HTML Help
class - Java class file
cpio - Cpio archive
cr2 - Canon Raw image file (v2)
cr3 - Canon Raw image file (v3)
crx - Google Chrome extension
cur - Icon file
dcm - DICOM Image File
deb - Debian package
dmg - Apple Disk Image
dng - Adobe Digital Negative image file
docx - Microsoft Word document
dsf - Sony DSD Stream File (DSF)
dwg - Autodesk CAD file
elf - Unix Executable and Linkable Format
eot - Embedded OpenType font
eps - Encapsulated PostScript
epub - E-book file
exe - Executable file
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
f4p - ISO base media file format protected by Adobe Access DRM used by Adobe Flash Player
f4v - ISO base media file format used by Adobe Flash Player
fbx - Filmbox is a proprietary file format used to provide interoperability between digital content creation apps.
flac - Free Lossless Audio Codec
flif - Free Lossless Image Format
flv - Flash video
gif - Graphics Interchange Format
glb - GL Transmission Format
gz - Archive file
heic - High Efficiency Image File Format
icc - ICC Profile
icns - Apple Icon image
ico - Windows icon file
ics - iCalendar
indd - Adobe InDesign document
it - Audio module format: Impulse Tracker
j2c - JPEG 2000
jls - Lossless/near-lossless compression standard for continuous-tone images
jp2 - JPEG 2000
jpg - Joint Photographic Experts Group image
jpm - JPEG 2000
jpx - JPEG 2000
jxl - JPEG XL image format
jxr - Joint Photographic Experts Group extended range
ktx - OpenGL and OpenGL ES textures
lnk - Microsoft Windows file shortcut
lz - Archive file
lzh - LZH archive
m4a - Audio-only MPEG-4 files
m4b - Audiobook and podcast MPEG-4 files, which also contain metadata including chapter markers, images, and hyperlinks
m4p - MPEG-4 files with audio streams encrypted by FairPlay Digital Rights Management as were sold through the iTunes Store
m4v - Video container format developed by Apple, which is very similar to the MP4 format
macho - Mach-O binary format
mid - Musical Instrument Digital Interface file
mie - Dedicated meta information format which supports storage of binary as well as textual meta information
mj2 - Motion JPEG 2000
mkv - Matroska video file
mobi - Mobipocket
mov - QuickTime video file
mp1 - MPEG-1 Audio Layer I
mp2 - MPEG-1 Audio Layer II
mp3 - Audio file
mp4 - MPEG-4 Part 14 video file
mpc - Musepack (SV7 & SV8)
mpg - MPEG-1 file
mts - MPEG-2 Transport Stream, both raw and Blu-ray Disc Audio-Video (BDAV) versions
mxf - Material Exchange Format
nef - Nikon Electronic Format image file
nes - Nintendo NES ROM
odp - OpenDocument for presentations
ods - OpenDocument for spreadsheets
odt - OpenDocument for word processing
oga - Audio file
ogg - Audio file
ogm - Audio file
ogv - Audio file
ogx - Audio file
opus - Audio file
orf - Olympus Raw image file
otf - OpenType font
parquet - Apache Parquet
pcap - Libpcap File Format
pdf - Portable Document Format
pgp - Pretty Good Privacy
png - Portable Network Graphics
pptx - Microsoft Powerpoint document
ps - Postscript
psd - Adobe Photoshop document
pst - Personal Storage Table file
qcp - Tagged and chunked data
raf - Fujifilm RAW image file
rar - Archive file
rpm - Red Hat Package Manager file
rtf - Rich Text Format
rw2 - Panasonic RAW image file
s3m - Audio module format: ScreamTracker 3
shp - Geospatial vector data format
skp - SketchUp
spx - Audio file
sqlite - SQLite file
stl - Standard Tesselated Geometry File Format (ASCII only)
swf - Adobe Flash Player file
tar - Tarball archive file
tif - Tagged Image file
ttf - TrueType font
vcf - vCard
voc - Creative Voice File
vsdx - Microsoft Visio File
vtt - WebVTT File (for video captions)
wasm - WebAssembly intermediate compiled format
wav - Waveform Audio file
webm - Web video file
webp - Web Picture format
woff - Web Open Font Format
woff2 - Web Open Font Format
wv - WavPack
xcf - eXperimental Computing Facility
xlsx - Microsoft Excel document
xm - Audio module format: FastTracker 2
xml - eXtensible Markup Language
xpi - XPInstall file
xz - Compressed file
zip - Archive file
zst - Archive file

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.

tokenizer

Type: ITokenizer

Usable as source of the examined file.

fileType

Type: FileTypeResult

An object having an ext (extension) and mime (mime type) property.

Detected by the standard detections or a previous custom detection. Undefined if no matching fileTypeResult could be found.

file-type-cli - CLI for this module
image-dimensions - Get the dimensions of an image

file type

Install

Usage

Node.js

Browser

API

fileTypeFromBuffer(buffer)

buffer

fileTypeFromFile(filePath)

filePath

fileTypeFromStream(stream)

stream

fileTypeFromBlob(blob)

blob

fileTypeFromTokenizer(tokenizer)

tokenizer

fileTypeStream(webStream, options?)

readableStream

options

sampleSize

Example

readableStream

supportedExtensions

supportedMimeTypes

Custom detectors

Abort signal

Supported file types

tokenizer

fileType

Related

Maintainers