You can use NSFW JS to identify indecent content without having files ever leave the client's machine, even defensively if you can't control the content being delivered. Ever see something that when you go to bed, those same images are there when you close your eyes? And I'm not talking about one of those good dreams, like Nicolas Cage or something, but the kind that if you have it on your screen when the boss walks by, you'll be looking for a new job. User input can be disgusting. One of my friends made their own online store back in the day, and it allowed for negative quantities. Malicious users would buy $50 of shirts, and then add MINUS $40 in shirts, effectively discounting their own orders!