Hello, Thank you for contacting MyThemeShop today. By default Rank Math uses Post permalink value for canonical url. You can add trailing slash in Permalink structure by Navigating to Dashboard >> Settings >> Permalinks:    If you only want to change canonical url without changing permalink structure then, please add below filter code in your theme's functions.php file: add_filter( 'rank_math/frontend/canonical', function( $url ) { return trailingslashit( $url