YouTube staff constantly reviews flagged videos to determine whether they violate the video-sharing website’s guidelines. Most videos that do are removed. Sometimes a video doesn’t violate the guidelines, but may not be appropriate for everyone. These videos are age-restricted.
When a video has been age-restricted, a warning screen is displayed and only users who are 18 or older can watch it. But if you’re not 18, and still want to watch an age-restricted video, you can either download the video (make sure the copyright of the video allows downloading), or bypass YouTube’s filters to watch it online. This method does not require you to login into your Google/YouTube account.
All YouTube videos’ URLs look like this:
http://www.youtube.com/watch?v=[some random characters]
Replace the “=” with a “/” and remove the “watch?”, so that the URL looks like this:
http://www.youtube.com/v/[some random characters]
Now enter the new URL in your browser. The video should now be fully playable. It will be embedded on your browser in full screen.
The reason this works is because for some reason the age verification screen doesn’t come up on embedded videos. This technique doesn’t work for videos blocked in your country.