Optimizely - A/B testing you'll actually use.
Google Analytics - Improve your website to increase conversions, improve the user experience, and make more money using Google Analytics. Measure, understand and quantify engagement on your site with customized and in-depth reports.
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.
Mixpanel - Mixpanel is the most advanced analytics platform in the world for mobile & web.
Matomo - Matomo is an open-source web analytics platform
Crazy Egg - Through Crazy Egg's heat map and scroll map reports you can get an understanding of how your visitors engage with your website so you can boost your conversion rates.