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readme.md

file-type

Detect the file type of a Buffer/Uint8Array

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

Install

$ npm install --save file-type

Usage

Node.js

const readChunk = require('read-chunk');
const fileType = require('file-type');
const buffer = readChunk.sync('unicorn.png', 0, 4100);

fileType(buffer);
//=> {ext: 'png', mime: 'image/png'}

Or from a remote location:

const http = require('http');
const fileType = require('file-type');
const url = 'http://assets-cdn.github.com/images/spinners/octocat-spinner-32.gif';

http.get(url, res => {
	res.once('data', chunk => {
		res.destroy();
		console.log(fileType(chunk));
		//=> {ext: 'gif', mime: 'image/gif'}
	});
});

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 no match.

input

Type: Buffer Uint8Array

It only needs the first 4100 bytes.

Supported file types

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.

file-type-cli - CLI for this module