SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Majestic - Majestic - Link intelligence tools for SEO and Internet PR and Marketing. Site Explorer shows inbound link and site summary data.
Lumar - (Previously DeepCrawl) Hosted SEO spider to analyze and find problems with websites.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
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.
Brightedge - BrightEdge is the leading content performance marketing platform, helping more than 1,200 customers generate more organic traffic. BrightEdge is based in San Mateo, CA with offices in New York, Seattle, Chicago, Tokyo, Sydney, and London.