Godwin’s law (also known as Godwin’s Rule of Nazi Analogies or Godwin’s Law of Nazi Analogies) is a humorous observation made by Mike Godwin in 1990 that has become an Internet adage. It states:
As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1.
In other words, Godwin observed that, given enough time, in any online discussion—regardless of topic or scope—someone inevitably criticizes some point made in the discussion by comparing it to beliefs held by Hitler and the Nazis. Godwin’s law is often cited in online discussions as a deterrent against the use of arguments in the widespread Reductio ad Hitlerum form.