Certain videos on YouTube, that contain either nudity, explicit language or violence, are put under the 18+ category and you cannot watch these videos* unless you sign-in to your YouTube /Google account and click Yes to the following warning:
[*] You will not get any adult videos on YouTube search results if you turn on Safety Mode.This video or group may contain content that is inappropriate for some users, as flagged by YouTube’s user community or as determined by the video uploader.
To view this YouTube video, verify you are 18 or older by signing in or signing up (link – http://www.youtube.com/verify_age?next_url=)
If you don’t have a Google account or if don’t want to log in to YouTube just for watching a video clip that has been flagged as NSFW by other viewers on YouTube, here’s how:
The YouTube video URL is like this:
http://www.youtube.com/watch?v=cAVxaLPU
If you replace "watch" in the YouTube URL with "watch_popup," the adult only video will immediately play inside your browser screen without any restrictions.
Related: YouTube Video not available in my country