Not safe for work (NSFW) is an Internet slang or shorthand used to mark URLs and hyperlinks which link to videos or websites pages that contain nudity, intense sexuality, profanity, violence or other potentially disturbing subject matter, which the viewer may not wish to be seen looking at in a public or formal environment, including a workplace, school or in a family setting.^[1][2] NSFW has particular relevance for people trying to make personal use of the Internet at workplaces or schools which have policies prohibiting access to sexual and graphic subject matter.^[3]

The similar expression not safe for life (NSFL) is also used, referring to content which is so nauseating or disturbing that it might be emotionally scarring to view. Links marked NSFL may contain fetish pornography, gore or lethal violence.^[4] NSFL may also stand for not safe for lunch, referring to vomiting induced by disturbing imagery.