Age restriction

An age-restricted video will not play for anyone signed out, anyone under 18, or anyone in Restricted Mode. Embeds elsewhere stop working too. The viewer gets bounced back to YouTube to sign in. Monetisation stays technically possible, though advertisers who avoid mature subject matter mean these videos often end up with limited ads or none. Creators can apply the restriction themselves. YouTube applies it at review when something breaches the guidelines for younger viewers without breaching them outright. Think of it as the middle setting between fully available and removed, and as a reach penalty that is easy to trigger and slow to undo.