Do it like this:
On webview set the default url like site.com?utm=app
Now in your website write a js code that get the url parameters, when you find utm parameter with value "app" set a cookie from js
Then check if the cookie exist before the ads js code, if it exists don't embed the code from ads(adsense or whatever you use), if not exist embed it.
Is the simplest way to do it but read the ads provider policy first and see if the ads display manipulation is forbidden or not.
L.E: this will work with the default webview, you will not need to search for other browser api's to implement the webview
