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.
Plerdy - Plerdy is a comprehensive conversation rate optimization software that caters to professional online marketers and agencies, allow them to enhance website performance and increase revenue greatly.
Backlinks by Neil Patel - A backlinks research tool for competitive intelligence
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
SmallSEOTools Google Cache Checker - Google Cache checker is an online tool to view cached pages, Enter any website URL to find when was the last time your web page was cached.