SISTRIX - SISTRIX toolbox is an SEO tool for professionals helping reputable companies to constantly improve their websites.
Optimizely - A/B testing you'll actually use.
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.
Page Weight - Find and fix heavy images on your website
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.