Arduino checkbox listener

how would i check if checkbox is on or off web server using an arduino ethernet shield v2?
ive tried many tutorials and none of them worked

check for the parameter "checked"

if you show us what you have currently, we might be able help.
Make a short demo sketch with a form and a checkbox and a function which should react on the state of the checkbox.
Only the basics - but the sketch must compile on a Uno.
The easier you make it for us to help - the sooner you get help.

how do i do that??