SEO Minion is one of those free tools that punches well above its weight. You click the toolbar icon on any page and you get an instant breakdown of the on-page SEO elements: title tag, meta description, heading structure, canonical URL, and all the meta robots directives. It’s the kind of information you’d otherwise have to dig through the browser developer tools to find, and SEO Minion surfaces it in seconds.
The hreflang checker is particularly useful if you work on international sites. Most browser extensions ignore hreflang entirely, which makes SEO Minion a rare find for anyone dealing with multilingual or multi-region websites. You can also run a broken link check from directly within the extension, which isn’t as thorough as a full crawl but is handy for quick spot-checks on a specific page.
I find the SERP preview feature useful when reviewing title tags and meta descriptions with clients. You can see exactly how a page is likely to appear in Google search results, which makes conversations about character limits and messaging much more concrete. The on-page highlighting mode, which visually marks up headings and links directly on the page, is a nice touch for client screen-shares. There are no limits on how much you can use it, no sign-up required, and no paid tier to worry about. It’s simply a well-made free tool.