Ahrefs is a software tool that is designed to help with SEO. The program allows website owners to research the search engine optimization of competitors. The data gleaned from the program can

Majestic - Link intelligence tools for SEO and Internet PR and Marketing. Site Explorer shows inbound link and site summary data.

Your website is like an iceberg: you can only see part of it. Some issues may be underneath the surface, affecting your visitor's experience and hurting your search engine rankings.