I'm sure OP meant that. Proxy through a server != return a redirect to the client. And as mentioned elsewhere, they're writing directly to GA using a documented API; unless they are sending data from the client to the backend using a query and path that look exactly like GA's (which, why?), there is no way to know what client requests are logging data (and that's assuming they're specific client requests, rather than being logged as part of the actual functional interactions, using a session store, which if Ublock tried to heuristically detect and block, would block actual user facing functionality)