Introduction
Please keep in mind that implementing, diagnosing, and debugging a custom configuration for mod_pagespeed are tasks that are best handled by a systems administrator with the skills, training, and expertise required to do so for you. Although these tasks are not related to cPanel or the basic configuration of cPanel, we would like to offer the following guide as a courtesy.
This guide goes over some techniques that can be used to debug and diagnose problems that you may encounter when optimizing mod_pagespeed for use on your cPanel server.
Turning Debug Output on via the Configuration File
If you'd like to get debug output for every request, you can turn it on by enabling the debug filter in your .htaccess file with the following:
<IfModule pagespeed_module>
ModPagespeedEnableFilters debug
# Check for an HTML comment at the very end of your site's HTML in the developer tools of your webbrowser
# Alternatively you can visit your site's URL with GET parameters instead of using the above configuration option:
# domain.tld/?ModPagespeed=on&ModPagespeedFilters=core,debug
</IfModule>
You can also add this configuration to other configuration files on your server:
What are the configuration file locations for mod_pagespeed on a cPanel server?
Turning Debug Output On Per Request
The mod_pagespeed module also allows you to enable, disable, and configure various options on a per request basis via GET parameters.
The following URL, when requested, would enable mod_pagespeed, enable the default optimizations, and produce debug output within the HTML of the page:
https://exampledomain.tld/?ModPagespeed=on&ModPagespeedFilters=core,debug
If you need more detailed information please see the official documentation: