The co-ordinated raids on 60 addresses were the first time the authorities had acted on this issue in such a way.
The aim is to tackle what police called "a substantial rise in verbal radicalism".
Typical crimes included "glorification of Nazism [and] xenophobic, anti-Semitic and other right-wing extremism", they said.
Holger Munch, president of Germany's federal criminal police authority, the Bundeskriminalamt (BKA) said: "Today's action makes it clear that police authorities of the federal and state governments act firmly against hate and incitement on the internet."