node package manager

file-type

Detect the file type of a Buffer/Uint8Array

file-type

Detect the file type of a Buffer/Uint8Array

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

$ npm install --save file-type
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'} 
    });
});
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();

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

Type: buffer (Node.js), uint8array

It only needs the first 262 bytes.

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.

MIT © Sindre Sorhus