When you're the best at what you do by a mile, there can only be one problem: complacency. YouTube has been practically synonymous with Internet videos for a long while, so they didn't need to work too much on improving themselves. However, recent numbers have shown that video viewing on Facebook is growing constantly, and may very soon prove to be an actual competitor to Google's service. This is probably why YouTube has decided to change things up a bit and started experimenting with its search bar.
Being totally honest, this tweak is not very spectacular. Basically it's as simple as removing the border from the search box, and switching the search button (the magnifying glass icon) from the right side of the search box to the left. However, what I actually find interesting is that these modifications seem very similar to the ones Facebook made on its own search bar. After all, imitation is the highest form of flattery.
The changes, which will work on all the major browsers (Mozilla Firefox, Google Chrome, Safari, Opera and Internet Explorer) are still in an experimental stage, so they aren't yet available to the general public. However if you want to see them quicker and don't mind dabbling with your browser's developer console, here's how to do it: launch the YouTube website, open the developer console and type this command line document.cookie="VISITOR_INFO1_LIVE=0pBX9w1K8gk; path=/; domain=.youtube.com";window.location.reload(); (just copy paste it). Now press Enter and close the console. To reverse the change simply open the console, type: document.cookie="VISITOR_INFO1_LIVE=; path=/; domain=.youtube.com";window.location.reload(); and after you press Enter everything should be back to normal.