The On-Page SEO Checker was developed to reveal errors that prevent certain pages from ranking high in SERPs. So, basically, SE Ranking evaluates a page to see how well it is optimized for a certain query. You’ll get a complete list of errors, regardless of whether they are small or critical.
How to find
Hover over the “Tools” tab and click “On-Page SEO Checker”. You can also hit the “Tools” module, hover your mouse over “On-Page Checker” and click “Open the tool”.