Safe for work ('''SFW'''), or alternativel … Safe for work ('''SFW'''), or alternatively known as Work safe ('''WS'''), is a way to let the user that is about to click that link know that the preceding image(s) is not obscene, violent, or anything otherwise mentally shocking. Work safe means that it is safe to look at from work, while working, or from school. In fact, SFW usually means that the following link is rated roughly PG-13 or under. The alternative is ('''NSFW''') and obviously means Not Safe For Work.
But in all seriousness, the things that are SFW are the things YOU deem SFW. It is up to YOU the user to decide if it is SFW. The ultimate "test" is to ask yourself "If I am in a work/school environment, do I want this to be on my screen?" nment, do I want this to be on my screen?"