Theme Scientist A/B Testing

Super clean, powerful app that lets you alternate between themes for split testing. Being able to customize an entirely separate theme gives you almost unlimited flexibility to tweak and test.

It tracks the views, add to carts, conversion rates, and provides statistical significance levels so you know when to choose the winning version.

The team behind the app are great, I hired them in the past to speed up my site and add lazy loading to images. They're very responsive, always improving and building new features and products based on suggestions.