SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
SISTRIX - SISTRIX toolbox is an SEO tool for professionals helping reputable companies to constantly improve their websites.
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
Website Checker Tech - WebsiteChecker.Tech is SaaS tool that detects SEO and availability issues of your website, making it easier for you to fix them.
Page Weight - Find and fix heavy images on your website