Code to “noindex” All Categories in WordPress

/* No Index All Categories */
add_action('wp_head', 'wpflt_header_function_condition_noindex_all_categories');
function wpflt_header_function_condition_noindex_all_categories(){
if ( is_category() ) { ?>
<meta name="robots" content="noindex" />
<?php }
};

This will add ‘noindex’ tag to all Category pages in WordPress. Search Engines will crawl these pages but won’t index.