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Plugin: Defer Contact Form 7 Scripts
<?php # -*- coding: utf-8 -*-
declare( encoding = 'UTF-8' );
* Plugin Name: Defer Contact Form 7 Scripts
* Description: Adds <code>defer='defer'</code> to enqueued javascripts.
* Version: 1.0
* Required: 3.3
* Author: Thomas Scholz
* Author URI:
* License: GPL
* License URI:
* Defer Scripts, Copyright (C) 2011 Thomas Scholz
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
! defined( 'ABSPATH' ) and exit;
if ( ! function_exists( 'add_defer_to_cf7' ) )
function add_defer_to_cf7( $url )
if ( // comment the following line out add 'defer' to all scripts
FALSE === strpos( $url, 'contact-form-7' ) or
FALSE === strpos( $url, '.js' )
{ // not our file
return $url;
// Must be a ', not "!
return "$url' defer='defer";
add_filter( 'clean_url', 'add_defer_to_cf7', 11, 1 );

Can you please specify which file/function this goes into? Thanks!

broros commented Oct 19, 2014

can we add async instead of defer? I tried adding it but it is placed at the end of the <script tag, It needs to be placed at the beginning to be effective

broros commented Oct 19, 2014

also this does not seem to work if i use esc_url, clean_url has been deprecated

How to install this?

diggy commented Jun 20, 2016

As of WP 4.1+ you can use the script_loader_tag filter hook, see Toscho's answer @

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