Remove taxonomy slugs (categories, post tags and custom taxonomies) from URL

add_filter('request', 'rudr_change_term_request', 1, 1 );

function rudr_change_term_request($query){
	
	$tax_name = 'product_cat'; // specify you taxonomy name here, it can be also 'category' or 'post_tag'
	
	// Request for child terms differs, we should make an additional check
	if( $query['attachment'] ) :
		$include_children = true;
		$name = $query['attachment'];
	else:
		$include_children = false;
		$name = $query['name'];
	endif;
	
	
	$term = get_term_by('slug', $name, $tax_name); // get the current term to make sure it exists
	
	if (isset($name) && $term && !is_wp_error($term)): // check it here
		
		if( $include_children ) {
			unset($query['attachment']);
			$parent = $term->parent;
			while( $parent ) {
				$parent_term = get_term( $parent, $tax_name);
				$name = $parent_term->slug . '/' . $name;
				$parent = $parent_term->parent;
			}
		} else {
			unset($query['name']);
		}
		
		switch( $tax_name ):
			case 'category':{
				$query['category_name'] = $name; // for categories
				break;
			}
			case 'post_tag':{
				$query['tag'] = $name; // for post tags
				break;
			}
			default:{
				$query[$tax_name] = $name; // for another taxonomies
				break;
			}
		endswitch;

	endif;
	
	return $query;
	
}


add_filter( 'term_link', 'rudr_term_permalink', 10, 3 );

function rudr_term_permalink( $url, $term, $taxonomy ){
	
	$taxonomy_name = 'product_cat'; // your taxonomy name here
	$taxonomy_slug = 'product_cat'; // the taxonomy slug can be different with the taxonomy name (like 'post_tag' and 'tag' )

	// exit the function if taxonomy slug is not in URL
	if ( strpos($url, $taxonomy_slug) === FALSE || $taxonomy != $taxonomy_name ) return $url;
	
	$url = str_replace('/' . $taxonomy_slug, '', $url);
	
	return $url;
}
 

add_action('template_redirect', 'rudr_old_term_redirect');

function rudr_old_term_redirect() {
	
	$taxonomy_name = 'product_cat';
	$taxonomy_slug = 'product_cat';
	
	// exit the redirect function if taxonomy slug is not in URL
	if( strpos( $_SERVER['REQUEST_URI'], $taxonomy_slug ) === FALSE)
		return;

	if( ( is_category() && $taxonomy_name=='category' ) || ( is_tag() && $taxonomy_name=='post_tag' ) || is_tax( $taxonomy_name ) ) :

        	wp_redirect( site_url( str_replace($taxonomy_slug, '', $_SERVER['REQUEST_URI']) ), 301 );
		exit();
		
	endif;

}