I'm not exactly sure why this has happened but until yesterday YouTube was working just fine. Then, the large player option on the video went out of proportion (literally) and is now way too big. I read somewhere that deleting cookies might solve this, and I tried it, but it didn't fix my issue.
Screenshots below represent the problem:
Normal size:
Large size:
As you can see from the large size image, the video is just way too big.
I'm using latest version of Chrome and Windows 8.1.
Best Answer
This is not a bug. YouTube is experimenting with a new player which is resizing the Player Dynamically. Read here: YouTube Experiment
Are you sure you deleted all your cookies ? Try this, launch your Chrome Browser in Incognito Mode (Ctrl+Shift+N) and go to YouTube and check if you still see the large player. If not than you did not clear the cookies properly.
Regular YouTube Player
To go back to the regular interface press Ctrl+Shift+J in Chrome and Copy/Paste in the console the following code:
Large YouTube Player
To set the large YouTube player press Ctrl+Shift+J in Chrome and paste the following code which will change the YouTube cookie: