Godwin's Law
Godwin's Rule of Nazi Analogies
The observed Internet phenomenon where if an online discussion (regardless of topic or scope) goes on long enough, sooner or later someone will compare someone or something to Hitler or Nazism.
Origin
American attorney Mike Godwin formulated the law in 1990 for Usenet newsgroups: "As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one." Godwin later explained that the law was not a prediction but a deliberate experiment in memetics — he wanted to create a social norm that would make people think twice before making glib Holocaust analogies. He discussed its origins in a 1994 Wired essay.
Everyday Use
Scroll far enough into any heated comment thread and someone will inevitably invoke Hitler or the Nazis. It's become such a reliable pattern that many online communities treat it as a signal the conversation is over — the person who made the comparison has run out of real arguments.