Free tool to check the "authority" of any website based on the quality and quantity of its external backlinks.| Ahrefs
Find the easiest keywords to rank for with our free Keyword Difficulty (KD) checker. No registration required.| Ahrefs
MozBar is a free browser extension that helps you perform SEO research on the go. Quickly assess the strength and authority of any website, easily spot technical issues, and analyze any domain with this easy-to-use toolbar.| Moz