Website Grader - Grade your website's strengths and weaknesses in seconds.
SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
PageSpeed Ninja - One-click page speed boost for WordPress
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
WebSite Auditor - The techie's SEO spider: find site issues other tools miss
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.