Split testing, also known as A/B or multi-variant testing, is a method of serving experimental iterations of your site to a sample of visitors to test their effectiveness before deciding to roll out changes to everyone. Netlify's Split Testing feature uses Branch Deploys to serve different versions of the site without compromising performance, by using the same infrastructure and handling URL updates for visitors. This allows for consistent user experiences during split tests and enables instant start and stop configurations via the Netlify Admin. With "branch affinity", visitors are consistently assigned to the same branch under a split test, ensuring they don't experience UI changes mid-navigate.