YouTube stuttering can be very frustrating and make certain videos practically unwatchable. There are many reasons why this may happen such as a slow or overtaxed computer, insufficient bandwith or even issues with the video service. Often however even with more common issues eliminated stuttering can still persist.
When stuttering is accompanied by tearing this is almost certainly an issue with flash player. In particular it is no able to sync the frames correctly which causes tearing and stuttering to appear. This does not usually happen with standard frame rate videos even in 1080p quality. It is quite common however with 60 fps footage of any resolution. The issue appears to happen only in or more often in full screen.
Thankfully it is possible to fix the issue by disabling flash player entirely. Navigate to chrome://plugins in Chrome browser. Find
Adobe Flash Player and click the disable link. Refresh the video page. The stutter and vsync tearing should now be gone. Restarting the browser is not normally required.
This method does have some caveats. For one certain websites still use flash player as the only playback option meaning the video will be unplayable. A workaround for this flash player can be enabled temporarily in these cases. The other issue is that disabling flash player plugin may not always work when a video is played in a second Chrome window as opposed to within a tab. If the issues appears in a new window when in full screen, moving the window to transform it to a tab in another window.