I see this popping up with increasing frequency on political subreddits, the claim that the Nazis were socialists. How true is that claim?
Heya! You might be interested in these earlier answers:
Additionally, /u/commiespaceinvader has some insightful answers on What is fascism, anyway?, the relationships between Nazism and fascism, and fascism in Nazi Germany versus Italy and Austria.
There are already some good answers here. I wanted to just add that I have also seen this popping up, too, and often enough to write a question about it and some related issues—specifically the related "claim" that Democrats (as in the US political party) are in league with the KKK.
I put "claim" in quotes because I'm pretty convinced this is part of the "meme magic" strategy of the "alt-right" trolling subculture. Meaning, I'm pretty sure that the people who started these ideas, if not the ones propagating them now, know the ideas are nonsense, and are doing it just to troll people who know history / confuse people who don't / poison the well so people will have a harder time verifying anything about these controversial themes, at least through the internet and resources like Ask Historians.