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Buffer HTML5 audio/video for uninterrupted playback.

Provides a workaround for Chrome's incorrect canplaythrough behaviour and adds some other useful functionality.


Native JavaScript, no dependencies.

Released under the MIT license, based on code by Denis Nazarov.

Uses code by Michael Zaporozhets, based on by Chad Smith.


var foo = new Mediabuffer(element, progressCallback, readyCallback[, disableMobileCheck[, forceFullDownload]]);

###element The <audio> or <video> element you want to buffer e.g. document.getElementById('example'). The media source should be defined before initialising Mediabuffer using the element's src attribute or <source> child elements.

###progressCallback Function to run as the media buffers. Takes a single parameter, percentBuffered which you can use to provide feedback to the user as the file buffers.

###readyCallback Function to run when the file is buffered. You'll probably want to use the element's play() function here.

###disableMobileCheck Optional boolean to disable the check for mobile browsers. Defaults to false.

###forceFullDownload Optional boolean to force the browser to buffer the whole media file before calling the readyCallback. Defaults to false.


function progress(percentBuffered) {
	console.log('Buffering: ' + percentBuffered + '%');

function ready() {

var mbExample = new Mediabuffer(document.getElementById('example'), progress, ready);

##Browser Compatibility Tested and working in Chrome 40, Firefox 35, Safari 7.1.3 (see notes), Opera 12.16 and Internet Explorer 9+. Should work in anything that supports HTML5 media elements, the preload attribute and the progress media event. Mobile browsers will fail gracefully by calling the readyCallback immediately due to the lack of preloading in the major mobile browsers.


  • Safari won't call the progressCallback if the buffer time is short, but it will call the readyCallback as expected.
  • Mobile browsers will only play media as the result of a user action so if you want your media to auto-play after buffering you'll need to make sure your .load() call is triggered by a user-initated event such as a click.

##Known issues

  • Mediabuffer works by measuring the element's download progress and estimating when it can be played back without further buffering. If a user's average download rate drops significantly after buffering completes they may still experience buffering towards the end of playback. If it's absolutely imperative that there is no chance of buffering, use the forceFullDownload option.
  • Chrome has a bugfeature that means it won't buffer past a certain point without a workaround. That's OK except that if you have controls visible they won't work as the user may expect and it can cause them to flicker between states. If you want to enable controls your best bet is to have them hidden initially and then show them in your readyCallback. For the best user feedback, you could replace your controls with an indicator of the loading status by using your progressCallback.

##Changelog v1.1 - added forceFullDownload option.

v1.0 - initial release.


Buffer HTML5 audio/video for uninterrupted playback.




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