Most of the best and most useful tools in this extension are NOT free - you must pay a monthy subscription fee for them. So....for me, that is a bait and switch tactic. If they were more explanatory and honest up front, they may get more subscribers...but if they are dishonest upfront, will you really believe the results they offer you after you pay up, or, will they ask for more money later on for a more "information-rich" result?!
The Ahrefs SEO Toolbar is a versatile free multi-tool for SEO professionals and webmasters, encompassing a range of valuable features such as on-page SEO report, broken link checker, redirect tracer, structured data checker, link highlighter, user-agent switcher, and country changer for search results
It also provides domain highlighter for SERPs and SEO metrics for paid subscribers