Nationals of Croatia and other EU/EEA countries do not need a residence permit to stay or work in Norway. However, if you want to stay for longer than three months, you must register with the police.
If you are a national of a non-EU/EEA country and want to work in Norway or to stay for longer than 90 days, you need a residence permit.
You will find information on the different types of residence permit on the homepage of UDI. You must first register your application in the Application Portal. You must gather all the documents in the relevant checklist on UDI's webpage.