the_content and is_main_query
To be honest, the function in_the_loop() is what you are looking for: add_filter( ‘the_content’, ‘custom_content’ ); function custom_content( $content ) { if ( in_the_loop() ) { // My custom content that I add to the_content() } return $content; } What in_the_loop does is to check if global for $wp_query (that is the main query object) … Read more