@malte

That's up to each individual country.

Full informative text: https://europa.eu/youreurope/citizens/travel/entry-exit/eu-citizen/index_en.htm

@malte
Within Schengen you have to be able to produce a valid Schengen ID when asked by police etc. Passports and national IDs that cover all the requirements (e.g. listing nationality)are options, but drivers licenses are usually not. This is part of the Schengen agreement.

Some countries have decided to trust some forms of ID from some other countries (I think Nordics are fine with each other's drivers licenses) in addition to this.