A flagged video will be reviewed by an administrator who has numerous options at hand including setting the flag for age verification which requires users to login before they can view the video. Age verification is pretty basic and anyone who cheated on his birthday can watch the video after logging in.
The message that gets displayed when a user who is not logged in loads a video with age verification is the following: “This video or group may contain content that is inappropriate for some users, as flagged by YouTube’s user community. To view this video or group, please verify you are 18 or older by signing in or signing up.”
The Firefox extension You Old Enough provides users with another way. The experimental add-on will check if the video on Youtube is flagged for age verification and open it immediately in a popup window.
CLICK HERE to downloadYou old enough firefox addon ..