My Left Ear Enjoyed This
Have you ever watched a video and the audio is only in one ear?

Did you wish you could make the audio play in both ears?

I had the same problem so I made this simple bookmarklet which makes the audio on any video play in both ears.

It works on YouTube, Vimeo, and most other video sites on the internet. Just add it to your bookmarks bar, navigate to the desired website, then click the "My Left Ear Enjoyed This" bookmark.

To install, simply drag and drop the button above into your bookmarks bar.
Once you've installed the bookmark, visit the video you want to view and click the bookmark.

Now both of your ears can enjoy this!
How does it work?
The bookmarklet works by injecting JavaScript code into the page you're currently viewing. This JavaScript code takes advantage of the Web Audio API by finding the currently playing video on the page, and combining both of the left and right audio channels. You can take a look at the full source code below.
c=new AudioContext(); v=document.getElementsByTagName('video'); a=c.createMediaElementSource(v[0]); c.destination.channelCount=1; a.connect(c.destination);
What if my browser doesn't have a bookmarks bar?
Most desktop browsers have a bookmarks bar, but it's possible that your browser is configured to hide the bookmarks bar. Here are a couple of shortcuts you can use to hide/show the bookmarks bar depending on your browser.

View → Toolbars → Bookmarks toolbar
Windows Chrome:
Ctrl + Shift + B
Mac Chrome:
⌘ + Shift + B
Internet Explorer:
Ctrl + Shift + B
⌘ + Shift + B
Who are you and why did you make this?
My name is Bryce Neal. I am a Software Engineer who watches way too much YouTube. I was watching a video about Game theory and the audio was playing in only one ear. I found this solution and I thought I would spread the word. You can follow me on Twitter if you like.