Do Germany passport holders need a visa to visit DK?

No visa. Germany and Denmark are both EU member states, so German citizens enjoy EU freedom of movement and may enter, stay, work, and study in Denmark without any visa, permit, or time limit. Travel with a valid German passport or national ID card. A German ordinary passport holder does not need a visa to visit Denmark. Both countries are members of the European Union and the Schengen Area, and German nationals exercise the EU right of free movement. This is not a Schengen 90/180-day visa-waiver situation (which applies to non-EU visa-exempt nationals such as Americans or Brazilians) but the stronger EU freedom-of-movement right: there is no cap on the length of stay, and a German citizen may also reside, work, and study in Denmark. For stays beyond three months, EU citizens register their residence with the Danish authorities (an administrative formality, not a visa). ETIAS, the EU travel authorisation system launching for visa-exempt non-EU travellers, does NOT apply to EU citizens. Because both states are in the Schengen Area, there are normally no systematic border checks at the German-Danish frontier, though Denmark has at times reintroduced temporary internal border controls and police may perform spot identity checks, so travellers should always carry a valid passport or EU national ID card. The travel document must be valid on the day of travel.