Who is the client?

How can i know if a card is render on desktop or on smartphone ?

Cards are specific to a dashboard. Card 1 from dash A can’t be opened on dash B. There is also no way to know who is logged into what dash. You can restrict a dash by setting it to admin only. There are ways around this or at least there were.

If someone changes something on a dash, that you will see from the service they called or the entity that was changed. This will give a user when you look at the entity log. It’s also fetchable through automations

Two mods that come to mind that may have this functionality or something close, browser mod and fully kiosk browser for android devices.

What is it you’re wanting to achieve? What do you want to be different based on whether the device is a desktop or phone? And then what do you want to do about a tablet in portrait (phone-like) or landscape (desktop-like)?

Personally I use lovelace_gen and set up different dashboards for phones and desktops, and then use the “set as default on this device” option. Then I use differently configured cards for each form factor when required. But that’s the exception - in most cases I’m using the same cards on both phone and desktop.

Hi. I need to know it because I want to display a stream video. On desktop the view is larger than higher, on smartphone in higher than larger. So, on desktop the stream will displayed as is, on smartphone rotated by 90 degree.