Smaller - Make your websites load faster
Website Grader - Grade your website's strengths and weaknesses in seconds.
Textalyzer - Analyze text readability and SEO parameters
PageSpeed Ninja - One-click page speed boost for WordPress
Screpy - Screpy is a web analysis tool that can analyze all pages of your websites in one dashboard and monitor them with your team. It's powered by Lighthouse and it also includes some different analysis tools (SEO, SERP, W3C, Uptime, etc).
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.