If you are a citizen of Finland, Iceland, Norway or Sweden, you are free to enter, live, study and work in Denmark. You do not need a visa or residence permit.
As a Nordic citizen, you can enter Denmark without a passport. However, you must be able to identify yourself if required, e.g. if you are staying in a hotel, camping ground, or the like. Your driver's license or bank card is sufficient identification.
Bringing your family
If your family members are Nordic citizens, they do not need to apply for family reunification. They can enter and reside in Denmark in accordance with the regulations for Nordic citizens.
If your family members are not Nordic citizens, they should either apply for a proof of registration or residence card under the EU rules.
Info Norden is the Nordic Council of Ministers' official information service for private persons and companies in the Nordic countries. The service is aimed at all citizens of the Nordic countries and is particularly relevant to students, jobseekers, persons who wish to move to another Nordic country, and companies which operate within the Nordic countries. Visit the website of Info Norden (available in English, Danish, Finnish, Icelandic, Norwegian and Swedish)