WP Chill

Silkalns

Brian Fegter

Chris Dillon

Razvan Aldea

For admins, developers, and support staff, Debug This provides a ton of information about your WordPress installation, all from the front-end admin bar.
<ul>
<li>The current WP_Query object</li>
<li>Blog info and options</li>
<li>Embed providers</li>
<li>Files in rendered HTML (CSS, images, JavaScript)</li>
<li>Filters and actions</li>
<li>Images sizes</li>
<li>Globals and constants</li>
<li>Menus</li>
<li>Object cache stats</li>
<li>Plugins, must-use plugins, and dropins</li>
<li>Rewrite rules</li>
<li>Queries</li>
<li>PHP and server information</li>
<li>Post attachments</li>
<li>Post types</li>
<li>Scripts and styles enqueued</li>
<li>Shortcodes</li>
<li>Sidebars and widgets</li>
<li>Taxonomies and terms</li>
<li>Themes</li>
<li>Users</li>
<li>WP cron schedules and jobs</li>
<li>WP debug log</li>
</ul>
Debug This helps you save time and effort when trying to figure out what’s going on. Instead of hardcoding debug snippets or writing complex unit 
tests for small functionality, you can simply bring to the surface what you need right from the admin bar.
For example, when viewing a single post, you can see:
<ul>
<li>a list of post attachments,</li>
<li>which menus and sidebars are being displayed,</li>
<li>the post type, post fields, and meta data,</li>
<li>the current query variables and query string,</li>
<li>the rewrite rules applied,</li>
<li>the author,</li>
<li>the terms,</li>
<li>and much more.</li>
</ul>
<h3>Extend</h3>
<h4>Debug This Functions</h4>
New debug modes can be created easily:
<pre><code>add_debug_extension(
 $mode,
 $menu_label,
 $description,
 $callback,
 $group = 'General'
);
</code></pre>
Example
<pre><code>add_debug_extension(
 'actions',
 __('Actions', 'debug-this'),
 __('$wp_actions contains all active registered actions', 'debug-this'),
 'foo_callback',
 'Filters And Actions'
);
function foo_callback($buffer, $template){
 global $wp_actions;
 $debug = print_r($wp_actions, true);
 return $debug;
}
</code></pre>
You can add links to the header of a debug mode page. Place this code within your debug callback function.
<pre><code>add_debug_header_link('http://urltolink', 'Link Label');
</code></pre>
Extensions can be removed as well using <code>remove_debug_extension($mode);</code>
No PRE Tags
If you don’t want your debug output to be enclosed in PRE tags, simply set the following in your extension:
<pre><code>Debug_This::$no_pre = true;
</code></pre>
Saved Queries and Execution Time
Retrieve saved queries and execution time by using the following static properties:
<ul>
<li><code>Debug_This::$execution_time</code></li>
<li><code>Debug_This::$queries</code> – SAVEQUERIES must defined as true</li>
</ul>
URL Helpers
<ul>
<li><code>Debug_This::get_current_debug_url()</code> – current URL with the debug query</li>
<li><code>Debug_This::get_escape_url()</code> – used for the debug escape link that links to original page URL</li>
</ul>
<h4>WP Actions</h4>
<ul>
<li><code>debug_this</code> – receives the $mode arg – outputs the debug code sent from the extension modes. The default action is set to priority 5. This allows you to prepend or append any output without conflict using less or greater priorities.</li>
</ul>
<h4>WP Filters</h4>
There are a few filters you can use to customize Debug This to your needs:
<ul>
<li><code>debug_this_template</code> – receives $template arg – Use your own template</li>
<li><code>debug_this_default_mode</code> – receives $mode arg – Alters the mode for the parent DT admin bar button link.</li>
<li><code>debug_this_output</code> – receives $output, $mode args – Filter debug content before it’s rendered</li>
</ul>
<h4>JavaScript</h4>
To access the built-in Debug This JS functionality, enqueue your custom script with the dependency set to <code>debug-this</code>. Your script will inherit a jQuery dependency.
Object: debugThis
<ul>
<li><code>debugThis.mode</code> – current mode</li>
<li><code>debugThis.defaultMode</code></li>
<li><code>debugThis.template</code> – current included template</li>
<li><code>debugThis.queryVar</code> – the defined query string variable</li>
</ul>
Functions:
<ul>
<li><code>isDebug()</code></li>
<li><code>getDebugMode()</code> – uses <code>isDebug()</code></li>
</ul>
Events:
A jQuery <code>debug-this</code> event is fired from the footer. You can hook into this event with the following;
<pre><code>jQuery(document).bind('debug-this', function(event, debugThis){
 console.log(debugThis);
});
</code></pre>
<h4>Helper Functions</h4>
There are three included functions to help you work with files.
<ul>
<li><code>debug_this_get_file_ownership($file)</code> – returns <code>array('name' => $name, 'group' => $group)</code></li>
<li><code>debug_this_get_file_perms($file)</code> – returns string – Example: 0775</li>
<li><code>debug_this_convert_perms_to_rwx($perms)</code> – returns string – converts permission number to RWX format – Example: 0755 folder becomes drwxr-xr-x</li>
</ul>

Debug This

Very nice, even the phpinfo() colors are displayed correctly.

Great plugin

Peek under the hood with sixty debugging reports just one click away.

Forge12 Interactive GmbH

F12 Profiler analyzes your WordPress site comprehensively and delivers concrete, prioritized recommendations to improve load times. The plugin combines server diagnostics, asset analysis, database optimization, and plugin impact assessment in a modern, clean interface.
<h4>Features</h4>
Analysis & Diagnostics
<ul>
<li>Server analysis (PHP, MySQL, OPcache, web server, SSL, HTTP/2, compression)</li>
<li>Automatic site crawler with load time measurement (desktop & mobile)</li>
<li>Asset analysis (CSS, JS, images) with optimization potential</li>
<li>OPcache status & configuration recommendations</li>
<li>PHP profiler (runtime, queries, hooks, plugin ranking, culprit analysis)</li>
<li>Plugin impact analysis (assets, hooks, queries per plugin)</li>
<li>PageSpeed Insights integration (Lighthouse Scores + Core Web Vitals + CrUX)</li>
<li>Performance score with 6 weighted categories (A-F grades, trend delta)</li>
<li>Recommendation engine with automatic optimization suggestions</li>
</ul>
Optimization Tools
<ul>
<li>Lazy Loading (images and iframes)</li>
<li>Font Display Optimization (font-display: swap/optional/fallback/block)</li>
<li>Script Defer Manager (automatic defer for scripts with exclusion list)</li>
<li>Auto Image Dimensions (prevents Layout Shifts / CLS)</li>
<li>HTML Minification (whitespace, comments, empty attributes)</li>
<li>CSS/JS Minification (file-based cache)</li>
<li>WordPress Bloat Removal (emojis, embeds, Dashicons, jQuery Migrate, XML-RPC, Heartbeat, and more)</li>
<li>Browser Cache (.htaccess-based)</li>
<li>DNS Prefetch & Preconnect (domain detection from asset scan)</li>
<li>Database Analysis (8 categories with detail view)</li>
<li>Autoload Manager (granular wp_options management)</li>
<li>Background Asset Scanner with conflict detection</li>
<li>File-based Page Cache with TTL and URL exclusion (Pro)</li>
<li>CSS/JS Asset Manager – disable, defer, async per page or globally (Pro)</li>
<li>Conditional Loading – shortcode, block, regex, archive, login status, post type, plugin (Pro)</li>
<li>Smart auto-suggestions with source-based plugin detection after full scan (Pro)</li>
<li>Asset Preload Manager – Link headers for critical assets (Pro)</li>
<li>Critical CSS Generator & Applier – above-the-fold CSS per template (Pro)</li>
<li>Unused CSS Removal – per page template, safelist, regex safelist (Pro)</li>
<li>WebP Image Conversion with batch queue and backup (Pro)</li>
<li>LQIP Image Placeholders – 20px blur-up previews with IntersectionObserver (Pro)</li>
<li>Preload Key Requests – LCP images, fonts, critical resources (Pro)</li>
<li>Script Delay – delays third-party JS until first user interaction (Pro)</li>
<li>Local Google Fonts – GDPR-compliant WOFF2 self-hosting (Pro)</li>
<li>YouTube/Vimeo Facade – thumbnail + play button instead of iframe (Pro)</li>
<li>Database Cleanup – one-click per category or bulk action (Pro)</li>
<li>Redis Object Cache Management – drop-in installation/removal (Pro)</li>
<li>Scheduled Crawls & Cleanups via WP-Cron (Pro)</li>
<li>Performance Budgets with email/webhook notifications (Pro)</li>
<li>Settings Import/Export as JSON (Pro)</li>
<li>One-Click Optimizer – automated optimization with backup & restore (Pro)</li>
<li>License Management with activation/deactivation (Pro)</li>
</ul>
User Interface
<ul>
<li>Modern iOS-style design system</li>
<li>React 18 + TypeScript SPA</li>
<li>30+ pages/tools with dedicated configuration</li>
<li>Context-sensitive info sections on all pages</li>
<li>Pro features visible with lock icon and upgrade prompt</li>
</ul>
<a href="https://www.forge12.com/f12-profiler-pro/" rel="nofollow ugc">Get F12 Profiler Pro</a>
<h4>System Requirements</h4>
<ul>
<li>WordPress 6.0 or higher</li>
<li>PHP 8.0 or higher</li>
<li>MySQL 5.7 / MariaDB 10.3 or higher</li>
</ul>

F12 Profiler

Excellent! After P3 doesn’t work with PHP7+ anymore, F12 seems finally the one stepping in to fill that gap.

Update [18-Jun-19]. After some small contributions of mine to the dev efforts, the plugin developer has decided to add me to the team, long after this review was written.

Finally an alternative to P3

Comprehensive WordPress performance analysis with crawling, load time measurement, server diagnostics, and integrated optimization tools. Free.

Debug This vs F12 Profiler