Ahrefs Backlink Checker - With the world's biggest index of live backlinks (over 15 trillion), Ahrefs Backlink Checker will show you the most complete backlink profile for any website.
Backlink Tool - A backlink tool to index your links quickly and freely.
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.
SEMScoop - Find and analyze easy to rank long-tail keywords with free SEMScoop Keyword Difficulty Tool, Start using them for SEO, PPC, content creation and all your marketing activities
PrepostSEO Broken Link Checker - Broken Link Checker - Find dead links on website
SEOReviewTools Backlinks Checker - Use the Free Backlink Checker to uncover ➽ Total Backlinks ➽ Linking Domains ➽ Discover: ① Who is linking to you ② Find new link building opportunities