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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'); // npm install read-chunk
const fileType = require('file-type');
const buffer = readChunk.sync('unicorn.png', 0, 262);

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(buffer)

Returns an Object (or null when no match) with:

ext - one of the supported file types
mime - the MIME type

buffer

Type: Buffer Uint8Array

It only needs the first 262 bytes.

Supported file types

SVG isn't included as it requires the whole file to be read, but you can get it here.

PR welcome for additional commonly used file types.

file-type-cli - CLI for this module