// Method 1: Filter. function my_acf_google_map_api( $api ){ $api['key'] = 'xxx'; return $api; } add_filter('acf/fields/google_map/api', 'my_acf_google_map_api'); // Method 2: Setting. function my_acf_init() { acf_update_setting('google_api_key', 'xxx'); } add_action('acf/init', 'my_acf_init');