SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
WP Rocket - WP Rocket offers a caching plugin for Wordpress.
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
Yoast - Yoast offers plugins to improve SEO and optimize web sites and blogs.
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.
Wordfence - Comprehensive security plugin for WordPress.