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.
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.
Pulno - SEO Audit and Website Analysis. Pull up your SEO.
RobinGupta Bulk Domain Authority Checker - Free tool to bulk check domain authority, Page Authority, Spam score & IP Address.
Fast Link Checker - An advanced tool to find broken links on web sites.
Backlink Tool - A backlink tool to index your links quickly and freely.