A B testing. 2 completely different sites. How to do?

Question

contextual advertising

There is a site that sells
But neither goals nor utm tags are configured there ... We pour ads and write orders in Excel.
They made a new version - completely different, but I'm afraid to launch it, because. not sure if it will work better.
It is necessary to make sure that the traffic is divided into both versions at the same time, then theoretically, according to the requests, it will be clear from where the sale was made, but ideally it would be better to see the price of this client.
Give me a direction where to dig...

Answer 1

I solved the issue using google experiment.

Answer 2

Visual Website Optimizer to help you
https://vwo.com/

Answer 3

nginx.org/ru/docs/http/ngx_http_split_clients_modu...