No, NSFW is visible without login or the URL parameter `showall=1`. This is a second level. YouTube has such a system too: https://support.google.com/youtube/answer/7458465?hl=en >#Limited features for certain videos > Hate speech is not allowed on YouTube. We remove content promoting violence or hatred against individuals or groups based on certain attributes. YouTube also doesn’t allow content intended to praise, promote, or aid violent criminal organizations. > Content that doesn’t violate our policies, but is close to the removal line and could be offensive to some viewers, may have some features disabled. > Content will remain available on YouTube, but the watch page will no longer have comments, suggested videos, or likes, and will be placed behind a warning message. These videos are also not eligible for ads. Having features disabled will not add a strike to your channel.