But do you want your country of residence to be Germany? It will limit you to 2 travel days in Germany.

Well yes and no, the plan is to buy 2 passes because I then live in the Netherlands (I only study in Germany for 1 Semester) and the other pass with the home country as Germany (because I register myself there as a resident too. So 1 pass I could use to explore Germany. And the other one to travel for example from Amsterdam/Rotterdam to London or Paris since otherwise I need to travel to Belgium first.

Even if you have Netherlands as your country of residence, you can travel in NL (including on the Eurostar/ Thalys) on two days during your pass.

Remember that the Eurostar passholder fare is €35 each way from NL. And on Thalys to Paris it’s €30 I think. You can often find cash tickets for not much more. So if you’re only interested in Paris and London, a pass isn't vital. (If you were planning a lot of travel in NL, then it would be)

I’m not sure what the rules are on temporary residence for choosing you COR, but it’s designed to stop you from using it as regular transport from your home.

I know about the 2 travel days, but I would probably then want to do 1 weekend to london and back, and 2 weeks later or so to paris and back. So that are 4 travel days. In that case, it would be easier to have a German global pass. But I don’t know if a German drivers license would proof residency.

The terms and conditions are here:

https://www.interrail.eu/en/terms-conditions/interrail-pass-conditions-of-use

It doesn’t mention driving licence, but ‘official residence documents issued by the government’. I think a driving licence would come under that, but you might be able to come up with some other documents in Germany.

But note that that will prevent you from more than 2 days in Germany.

If you’re trying to call your COR Germany when it’s really NL, then they might smell a rat and they’d be within their rights to switch your COR. 

Well I stay in Germany for 4 to at max 6 months so it would not be a lie if I mention Germany as my Country of Residence. Since I live during holidays and after the semester in NL both countries could be the COR I guess.

Consider the role of the inspector - he is only wanting to ensure you are the person in the pass, it is valid and not being used fraudulently. The app is rigorous at only allowing 2 days travel in your declared country of residence so unless he is suspicious that will satisfy him.

Obviously a Dutch or German inspector would easily detect your country of origin from your speech and if you were in Holland with a declared country of residence of Germany he might challenge it and you would need to show him some credible evidence of residence in Germany. Obviously there are official residential documents for long term residents, but as long as the evidence you show can only be gained if you have a “permanent” address then he is highly unlikely to worry - he has a full train to check.

So anything with a photo ID such as a student ID for a German College or a driving licence or an extended rental agreement would suffice. 

I believe the guidance is your “new” Country of Residence should have been your home for over 6 months.

Obviously if you have a Dutch passport or ID there is no issue on you declaring the Netherlands as your COR for unlimited travel in Germany as your evidence to a German inspector of your COR is unequivocal.

Allright, so in conclusion when I transfer my dutch drivers license to a german one I can use Germany as the country of residence?

Are you asking whether a driving license will help you convince a conductor? Maybe.

Having a driving licence doesn’t make your COR Germany, especially as it seems you will be there for less than 6 months.

I think you would be better to ask Eurail about your specific circumstances, to get a definitive answer. Otherwise you could be deemed to be travelling without a ticket. It may be that they’re perfectly happy for you to buy two passes with two CORs

Additionally, for just a return trip from the Netherlands to London and Paris, I'm not sure whether a pass would really pay off, because of the quite expensive pass reservations. Be sure to check regular fares.

No, you can't. I have just asked Customer Support and a driver's licence is not a valid proof of residency. Please see the entire answer below. 

"Dear Anna, 
 
Thank you for your message. 
 
Please note that a driver's license or an e-residency document is not a valid travel document.
Please check the following page for more information: https://www.interrail.eu/en/support/interested-in-interrailing/do-i-need-an-interrail-or-eurail-pass
 
Thank you and have a nice day! 

Best regards,

Mansur
Customer service team"

Allright then it’s clear I should have a different form of proof of registration. Thank you all for your answers!

I asked Customer Support for a clarification of what a valid proof of residency would be and here's the answer:

"A driver's license is not a valid proof of residency. A valid proof of residency would be an official government issued document confirming your residency in Germany."

It’s clear now that a drivers license is not a valid proof of residency. But I just don’t understand why they made that choice since a country only issues a driver license to people who are living in the country and it often has the municipality who is issuing on the driver license itself.