Judges in the western city of Stuttgart said the 29-year-old, identified only as Ralph K., who for several years ran the German-language “Altermedia Deutschland” site, “had led a criminal organization and propagated hate”.
Three co-defendants were convicted of contributing to the far-right platform and were handed suspended sentences between eight months and two years, national news agency DPA reported.
The German government shut down “Altermedia” on Holocaust Remembrance Day two years ago following a series of police raids.
Until then, “Altermedia” had been one of Germany's most popular online platforms for the far-right, attracting some five million visitors.
Prosecutors at the time said the site's content ranged from “incitement of violence against foreigners… to disparagement of people of other faiths and skin colours to Holocaust denial”.
It also included “banned Nazi greetings and slogans”, they said.
The website, hosted on servers in Russia, has been linked to US white supremacist and former Ku Klux Klan member David Duke.