From next Monday, new rules will apply to entry from Germany to the Netherlands: a 3G certificate must be provided.

Travelers must then show a negative corona test or prove that they are fully vaccinated or have recovered. Children under the age of 12 are exempt from this rule. The reason for the change is the worsened corona situation in Germany, as the Foreign Ministry announced in The Hague.
In the future, anyone flying to the Netherlands by plane will have to fill out a health declaration beforehand and have it with them. Vaccinated Dutch people are also advised to undergo a rapid test when they return from Germany. Most recently, there were no particular restrictions when entering the Netherlands from Germany. This is reported, among other things, by the Tagesschau.