file-type

Variables

• supportedExtensions
• supportedMimeTypes

Functions

• fileTypeFromBlob()
• fileTypeFromBuffer()
• fileTypeFromFile()
• fileTypeFromStream()
• fileTypeFromTokenizer()
• fileTypeStream()

Classes

• FileTypeParser

  • fromFile()
  • fromStream()
  • toDetectionStream()
• TokenizerPositionError

Type Aliases

• AnyWebReadableByteStreamWithFileType
• AnyWebReadableStream
• Detector
• FileTypeOptions
• FileTypeResult
• ReadableStreamWithFileType
• StreamOptions

variable supportedExtensions

const supportedExtensions: ReadonlySet<string>;

• Supported file extensions.

variable supportedMimeTypes

const supportedMimeTypes: ReadonlySet<string>;

• Supported MIME types.

function fileTypeFromBlob

fileTypeFromBlob: (
    blob: Blob,
    options?: FileTypeOptions
) => Promise<FileTypeResult | undefined>;

• Detect the file type of a [Blob](https://nodejs.org/api/buffer.html#class-blob) or [File](https://developer.mozilla.org/en-US/docs/Web/API/File).

  Parameter blob

  The [Blob](https://nodejs.org/api/buffer.html#class-blob) used for file detection.

  Parameter options

  Options to override default behavior.

  Returns

  The detected file type, or undefined when there is no match.

  Example 1

  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'}

function fileTypeFromBuffer

fileTypeFromBuffer: (
    buffer: Uint8Array | ArrayBuffer,
    options?: FileTypeOptions
) => Promise<FileTypeResult | undefined>;

• Detect the file type of a Uint8Array or ArrayBuffer.

  The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.

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

  Parameter buffer

  An Uint8Array or ArrayBuffer representing file data. It works best if the buffer contains the entire file. It may work with a smaller portion as well.

  Parameter options

  Options to override default behavior.

  Returns

  The detected file type, or undefined when there is no match.

function fileTypeFromFile

fileTypeFromFile: (
    filePath: string,
    options?: FileTypeOptions
) => Promise<FileTypeResult | undefined>;

• Detect the file type of a file path.

  The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the file.

  This is for Node.js only.

  To read from a [File](https://developer.mozilla.org/docs/Web/API/File), see fileTypeFromBlob().

  The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.

  Returns

  The detected file type and MIME type or undefined when there is no match.

function fileTypeFromStream

fileTypeFromStream: (
    stream: AnyWebReadableStream<Uint8Array> | NodeReadableStream,
    options?: FileTypeOptions
) => Promise<FileTypeResult | undefined>;

• Detect the file type of a [web ReadableStream](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream).

  If the engine is Node.js, this may also be a [Node.js stream.Readable](https://nodejs.org/api/stream.html#stream_class_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()](https://nodejs.org/api/stream.html#streamreadabletowebstreamreadable-options)).

  The file type is detected by checking the [magic number](https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files) of the buffer.

  Parameter stream

  A [web ReadableStream](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) or [Node.js stream.Readable](https://nodejs.org/api/stream.html#stream_class_stream_readable) streaming a file to examine.

  Parameter options

  Options to override default behaviour.

  Returns

  A Promise for an object with the detected file type, or undefined when there is no match.

function fileTypeFromTokenizer

fileTypeFromTokenizer: (
    tokenizer: ITokenizer,
    options?: FileTypeOptions
) => Promise<FileTypeResult | undefined>;

• Detect the file type from an [ITokenizer](https://github.com/Borewit/strtok3#tokenizer) 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.

  Parameter tokenizer

  File source implementing the tokenizer interface.

  Parameter options

  Options to override default behavior.

  Returns

  The detected file type, or undefined when there is no match.

  An example is [@tokenizer/http](https://github.com/Borewit/tokenizer-http), which requests data using [HTTP-range-requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests). A difference with a conventional stream and the [*tokenizer*](https://github.com/Borewit/strtok3#tokenizer), is that it is able to *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.

  Example 1

  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'}

function fileTypeStream

fileTypeStream: {
    (
        readableStream: NodeReadableStream,
        options?: FileTypeOptions & StreamOptions
    ): Promise<ReadableStreamWithFileType>;
    (
        webStream: AnyWebByteStream,
        options?: FileTypeOptions & StreamOptions
    ): Promise<any>;
};

• 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.

  Parameter readableStream

  A [web ReadableStream](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) or [Node.js stream.Readable](https://nodejs.org/api/stream.html#stream_class_stream_readable), streaming a file to examine.

  Parameter options

  May be used to override the default sample size.

  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().

  Example 1

  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)
  }

type AnyWebReadableByteStreamWithFileType

type AnyWebReadableByteStreamWithFileType = AnyWebReadableStream<Uint8Array> & {
    readonly fileType?: FileTypeResult;
};

type AnyWebReadableStream

type AnyWebReadableStream<G> = WebReadableStream<G> | ReadableStream<G>;

• Either the Node.js ReadableStream or the lib.dom.d.ts ReadableStream. Related issue: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/60377

type Detector

type Detector = {
    id: string;
    detect: (
        tokenizer: ITokenizer,
        fileType?: FileTypeResult
    ) => Promise<FileTypeResult | undefined>;
};

• A custom file type detector.

  Custom file type detectors are plugins designed to extend the default detection capabilities. They allow support for uncommon file types, non-binary formats, or customized detection behavior.

  Detectors can be added via the constructor options or by modifying FileTypeParser#detectors directly. Detectors provided through the constructor are executed before the default ones.

  Detectors can be added via the constructor options or by directly modifying FileTypeParser#detectors.

  ### Example adding a detector

  import {FileTypeParser} from 'file-type';
  import {detectXml} from '@file-type/xml';
  
  const parser = new FileTypeParser({customDetectors: [detectXml]});
  const fileType = await parser.fromFile('sample.kml');
  console.log(fileType);

  ### Available-third party file-type detectors

  - [@file-type/xml](https://github.com/Borewit/file-type-xml): Detects common XML file types, such as GLM, KML, MusicXML, RSS, SVG, and XHTML

  ### Detector execution flow

  If a detector returns undefined, the following rules apply:

  1. **No Tokenizer Interaction**: If the detector does not modify the tokenizer's position, the next detector in the sequence is executed. 2. **Tokenizer Interaction**: If the detector modifies the tokenizer's position (tokenizer.position is advanced), no further detectors are executed. In this case, the file type remains undefined, as subsequent detectors cannot evaluate the content. This is an exceptional scenario, as it prevents any other detectors from determining the file type.

  ### Example writing a custom detector

  Below is an example of a custom detector array. This can be passed to the FileTypeParser via the fileTypeOptions argument.

  import {FileTypeParser} from 'file-type';
  
  const customDetectors = [
  	async tokenizer => {
  		const unicornHeader = [85, 78, 73, 67, 79, 82, 78]; // "UNICORN" in ASCII decimal
  
  		const buffer = new Uint8Array(unicornHeader.length);
  		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([85, 78, 73, 67, 79, 82, 78]);
  const parser = new FileTypeParser({customDetectors});
  const fileType = await parser.fromBuffer(buffer);
  console.log(fileType); // {ext: 'unicorn', mime: 'application/unicorn'}

  Parameter tokenizer

  The [tokenizer](https://github.com/Borewit/strtok3#tokenizer) used to read file content.

  Parameter fileType

  The file type detected by standard or previous custom detectors, or undefined if no match is found.

  Returns

  The detected file type, or undefined if no match is found.

type FileTypeOptions

type FileTypeOptions = {
    customDetectors?: Iterable<Detector>;

    /**
	Specifies the byte tolerance for locating the first MPEG audio frame (e.g. `.mp1`, `.mp2`, `.mp3`, `.aac`).

	Allows detection to handle slight sync offsets between the expected and actual frame start. Common in malformed or incorrectly muxed files, which, while technically invalid, do occur in the wild.

	A tolerance of 10 bytes covers most cases.

 	@default 0
	*/
    mpegOffsetTolerance?: number;
};

type FileTypeResult

type FileTypeResult = {
    /**
	One of the supported [file types](https://github.com/sindresorhus/file-type#supported-file-types).
	*/
    readonly ext: string;

    /**
	The detected [MIME type](https://en.wikipedia.org/wiki/Internet_media_type).
	*/
    readonly mime: string;
};

type ReadableStreamWithFileType

type ReadableStreamWithFileType = NodeReadableStream & {
    readonly fileType?: FileTypeResult;
};

type StreamOptions

type StreamOptions = {
    /**
	The default sample size in bytes.

	@default 4100
	*/
    readonly sampleSize?: number;
};