How to get url fragment in controller?

url.com/controller/action#param1=x&param2=y Imagine such a url, when the request comes to a controller.

How to access the anchor parameters in controller’s action ?

As far as I understand the concept of urls, the part behind the „#“ is only client side and not server side. So you can acces it with javascript in the Storefront, but not in PHP, since the server only gets the url /action.

www.url.de? serverside # clientside

Yes, I was also sure about that, but was interested in whether there are any bypass methods.