Vaadin Website does not scale correctly if connected via DNS Frame Redirect

Hello together,

Background information:
Im using Vaadin 14 with Springboot as base.

I found out something confusing.
If I’m connecting to the IP-Address of my own website with my phone it scales as it should scale on a phone.
=> Everything is scaled up so that the end-user can easily navigate through the page. (No Desktop View)

If I’m now connecting with my phone to my own website with an external domain name including an Frame Redirect, then everything gets displayed in the common desktop view. Its the same view, which you would get with the “Desktop View” option enabled in the browser of the phone.

Does anyone know how this can happen or how I can fix this?
I want my website to look good on windows and on a mobile device.

My hunch is that the viewport meta tag would need to be applied also for the hosting frame. Exactly how you do that depends on the hosting solution you’re using, but the essence is that the top-level document needs to contain something along the lines of <meta name="viewport" content="width=device-width, initial-scale=1">.