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mp4.js - Javascript MP4 tag parser

mp4.js is a JavaScript library for reading and parsing metatags of MP4 files (m4a,m4v,ALAC). mp4.js can parse metadata within a browser or Node environment. It also supports reading from local files (Node-only), same-origin URLs (AJAX) and File instances (HTML5 File API).

Compatibility for AJAX/FileReaderAPI and nodejs is taken from [](43081j's ID3.js), implementation details are based upon the magnificent taglib, thanks for that!


<script src="mp4.min.js"></script>
<script type="text/javascript">
mp4('/audio/track.m4a', function(err, tags) {
    // tags now contains tags 

Here the MP4 is being requested by partial AJAX requests, such that only the metatags are read rather than the file as a whole.

Local Files

First, install mp4.js using NPM, the Node package manager.

npm install mp4js

Then use it like so:

var mp4 = require('mp4js');
mp4({ file: './track.m4a', type: 'local' }, function(err, tags) {
    // tags now contains your MP4 tags 

Note that here, the type is set to 'local' directly so that mp4.js will attempt to read from the local file-system using fs.

This will only work under NodeJS.

File API (HTML5)

<script src="mp4.min.js"></script>
<script type="text/javascript">
document.querySelector('input[type="file"]').onchange = function(e) {
    mp4(this.files[0], function(err, tags) {
        // tags now contains your MP4 tags 

This will read the data from the File instance using slices, so the entire file is not loaded into memory but rather only the tags.


Tags are passed as an object of the following format:

    "artist": "Song artist",
    "title": "Song name",
    "album": "Song album",
    "year": "2013",
    "date": "2013-01-10T20:20:10Z",
    "tracknumber": [2, 18]
    "track": "2/18"

The artist, title, album and year properties will always exist, though they will default to null.


On occasion, an MP4 may have an image embedded in the metatag. If this is the case, it will be available through cover. This has a structure like so:

FIXME (the API does not pass the MP4 cover through yet, but parsing of covers is ready)

    "type": "cover-front",
    "mime": "image/jpeg",
    "description": null,
    "data": ArrayBuffer

As you can see, the data is provided as an ArrayBuffer. To access it, you may use a DataView or typed array such as Uint8Array.