SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
SEOmator - SEO website analysis & audit tool
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
Ahrefs - Ahrefs is a toolset for SEO and marketing. We have tools for backlink research, organic traffic research, keyword research, content marketing & more. Give Ahrefs a try!
SiteGuru - SiteGuru crawls and analyzes your website. We check your content, links and website structure and give actionable tips to improve your site.