With Accessibility PRO active, every save of a post or page is checked and the findings appear in the Accessibility check box on the edit screen, marked must-fix or worth fixing. The checks: pictures with no alt text; alt text that is a file name; headings out of order; a second H1; empty headings; links with no text; links that say click here, read more or here; buttons with no text; embedded frames with no name; tables with no header row; form fields with no label; media that plays by itself with sound; video with no captions track. Check now checks what is in the editor this second, saved or not. Check every published page, on the Checker tab, runs the same checks over the whole site in batches and lists the pages that need attention with a link straight to each. Run it after a big import or once a month. The checker reads the normal WordPress editor content. Pages built inside a page builder get the reading tools but are not checked.