Nelio A/B Testing adds a tracking script at the very beginning of your website’s HTML structure. We do this so that it (hopefully) runs before any other scripts, including Google Analytics.

When our tracking script runs, the first thing it does is check if the current page is under test. If it is, it performs a JavaScript redirection to a different URL that will include some testing parameters in your URLs.

These parameters tell Nelio A/B Testing which variant has to be loaded for each visitor. You can know more about these parameters here.