Sexually explicit content like pornography is not allowed. Videos containing fetish content will be removed or age-restricted depending on the severity of the act in question. In most cases, violent, graphic, or humiliating fetishes are not allowed to be shown on YouTube.
In cases where videos do not cross the line, but still contain sexual content, YouTube may apply an age-restriction so that only viewers over a certain age can view the content.
Videos containing nudity or dramatized sexual conduct may be age-restricted when the context is appropriately educational, documentary, scientific or artistic. Videos featuring individuals in minimal or revealing clothing may also be age-restricted if they're intended to be sexually provocative, but don't show explicit content.
See YouTube's Policy Center for more info about nudity and sexual content.
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