If you would like to set up a split test and the target URLs contain optional parameters, you will have to use the option “regular expression” to set up your redirection.
Suppose that you want to redirect the page "http://www.example.com" to "http://www.example.com/variation". You also use Google Analytics tracking parameters to track your traffic acquisition sources. You therefore want the URL "http://www.example.com/?utm_medium=email&utm_source=newsletter" to redirect to "http://www.example.com/variation?utm_medium=email&utm_source=newsletter".
To achieve this, you must set up the test in the same way as we present below, ticking the box “Keep url parameters”.