John Blackbourn

<p>Query Monitor is the developer tools panel for WordPress and WooCommerce. It enables debugging of database queries, PHP errors, hooks and actions, block editor blocks, enqueued scripts and stylesheets, HTTP API calls, and more.</p>
<p>It includes some advanced features such as debugging of Ajax calls, REST API calls, user capability checks, and full support for block themes and full site editing. It includes the ability to narrow down much of its output by plugin or theme, allowing you to quickly determine poorly performing plugins, themes, or functions.</p>
<p>Query Monitor focuses heavily on presenting its information in a useful manner, for example by showing aggregate database queries grouped by the plugins, themes, or functions that are responsible for them. It adds an admin toolbar menu showing an overview of the current page, with complete debugging information shown in panels once you select a menu item.</p>
<p>Query Monitor supports versions of WordPress up to three years old, and PHP version 7.4 or higher.</p>
<p>For complete information, please see <a href="https://querymonitor.com/" rel="nofollow ugc">the Query Monitor website</a>.</p>
<p>Here’s an overview of what’s shown for each page load:</p>
<ul>
<li>Database queries, including notifications for slow, duplicate, or erroneous queries. Allows filtering by query type (<code>SELECT</code>, <code>UPDATE</code>, <code>DELETE</code>, etc), responsible component (plugin, theme, WordPress core), and calling function, and provides separate aggregate views for each.</li>
<li>The template filename, the complete template hierarchy, and names of all template parts that were loaded or not loaded (for block themes and classic themes).</li>
<li>PHP errors presented nicely along with their responsible component and call stack, and a visible warning in the admin toolbar.</li>
<li>Usage of “Doing it Wrong” or “Deprecated” functionality in the code on your site.</li>
<li>Blocks and associated properties within post content and within full site editing (FSE).</li>
<li>Matched rewrite rules, associated query strings, and query vars.</li>
<li>Enqueued scripts and stylesheets, along with their dependencies, dependents, and alerts for broken dependencies.</li>
<li>Language settings and loaded translation files (MO files and JSON files) for each text domain.</li>
<li>HTTP API requests, with response code, responsible component, and time taken, with alerts for failed or erroneous requests.</li>
<li>User capability checks, along with the result and any parameters passed to the capability check.</li>
<li>Environment information, including detailed information about PHP, the database, WordPress, and the web server.</li>
<li>The values of all WordPress conditional functions such as <code>is_single()</code>, <code>is_home()</code>, etc.</li>
<li>Transients that were updated.</li>
<li>Usage of <code>switch_to_blog()</code> and <code>restore_current_blog()</code> on Multisite installations.</li>
</ul>
<p>In addition:</p>
<ul>
<li>Whenever a redirect occurs, Query Monitor adds an HTTP header containing the call stack, so you can use your favourite HTTP inspector or browser developer tools to trace what triggered the redirect.</li>
<li>The response from any jQuery-initiated Ajax request on the page will contain various debugging information in its headers. PHP errors also get output to the browser’s developer console.</li>
<li>The response from an authenticated WordPress REST API request will contain an overview of performance information and PHP errors in its headers, as long as the authenticated user has permission to view Query Monitor’s output. An <a href="https://developer.wordpress.org/rest-api/using-the-rest-api/global-parameters/#_envelope" rel="nofollow ugc">an enveloped REST API request</a> will include even more debugging information in the <code>qm</code> property of the response.</li>
</ul>
<p>By default, Query Monitor’s output is only shown to Administrators on single-site installations, and Super Admins on Multisite installations.</p>
<p>In addition to this, you can set an authentication cookie which allows you to view Query Monitor output when you’re not logged in (or if you’re logged in as a non-Administrator). See the Settings panel for details.</p>
<h3>Other Plugins</h3>
<p>I maintain several other plugins for developers. Check them out:</p>
<ul>
<li><a href="https://wordpress.org/plugins/user-switching/" rel="ugc">User Switching</a> provides instant switching between user accounts in WordPress.</li>
<li><a href="https://wordpress.org/plugins/wp-crontrol/" rel="ugc">WP Crontrol</a> lets you view and control what’s happening in the WP-Cron system</li>
</ul>
<h3>Thanks</h3>
<p>The time that I spend maintaining this plugin and others is in part sponsored by:</p>
<ul>
<li><a href="https://automattic.com/" rel="nofollow ugc">Automattic</a></li>
<li><a href="https://servmask.com/" rel="nofollow ugc">ServMask</a></li>
<li><a href="https://wp-staging.com/" rel="nofollow ugc">WP Staging</a></li>
<li><a href="https://github.com/sponsors/johnbillion" rel="nofollow ugc">All my kind sponsors on GitHub</a></li>
</ul>
<h3>Privacy Statement</h3>
<p>Query Monitor is private by default and always will be. It does not persistently store any of the data that it collects. It does not send data to any third party, nor does it include any third party resources. <a href="https://querymonitor.com/privacy/" rel="nofollow ugc">Query Monitor’s full privacy statement can be found here</a>.</p>
<h3>Accessibility Statement</h3>
<p>Query Monitor aims to be fully accessible to all of its users. <a href="https://querymonitor.com/accessibility/" rel="nofollow ugc">Query Monitor’s full accessibility statement can be found here</a>.</p>


Query Monitor

If you are a WordPress Developer, this should be the first plugin that you should install.

Must have!


...it would be nice to have an option to deactivate the plugin on mobile devices. I noticed that it slows down the loading and time to be able to interact with the pages significantly. Sure, sometimes it would be useful to have it on mobile as well, and that could be added as an option.Otherwise it's a great, no the best plugin for that use case 😀👍 


Great, just one thing...


One of my must haves for plugin development from the beginning. 


Must have


Thank you for this ingenious plugin. It has already saved me hours of work debugging. It is also extremely helpful when optimising your own plugins. I have never had any problems with Query Monitor. I can only recommend it to every developer to use it as well.


Perfect for Debugging


The best debugging plugin for Wordpress dev. It gives a huge wealth of information about what’s going on under the hood. A must have for debugging queries and finding out simple bits of server information.


A must have for WP developer


Essential for any WP dev and debugging!


The Best WP Debug Plugin and Great Support


I use this plugin almost every day. Saved my time a hundred times.


Absolutely must have for WP development


Amazing tool. Beyond belief this is free.


Wordpress ecosystem at its best


At first impressions it looks like what the browser does.


Good plugin

Excellent plugin!


Query Monitor is an incredibly useful tool for developers and site administrators. It provides detailed insights into database queries, page load times, and resource consumption, making it a must-have for debugging and performance optimization.



I particularly appreciate how it highlights potential errors in the code and plugins during development, saving time and effort in troubleshooting. Its intuitive interface and in-depth reports make identifying issues straightforward.



Overall, it’s a fantastic plugin that I highly recommend to anyone building or maintaining WordPress websites.


Essential for Debugging and Performance Monitoring


It is a fantastic plugin, been using this for long.


Thanks for this.

best

Useful plugin


Sometimes you feel like your site is a black box and that is something that Query Monitor solves.  It provides insight into what is happening, shows errors, and gives you stats and timings for the page load process.  This helps in tracking down problems, in picking which plugins are the most performant, and when developing, to see what templates are being loaded.  Amazing plugin, for free.  Thank you John Blackbourn! 


An Amazing Tool

Query Monitor is the developer tools panel for WordPress and WooCommerce.

Milan Petrovic

<p>DebugPress is an easy-to-use plugin implementing popup for debugging and profiling currently loaded WordPress powered website page with support for intercepting AJAX requests. The main debugger window is displayed as a popup, activated through the button with the Bug integrated into WordPress Toolbar, or floating on the page.</p>
<p>The plugin currently has a total of 22 tabs in the popup debugger window, showing all kinds of information relevant to the current page, WordPress setup, background AJAX calls, and much more.</p>
<p>The plugin doesn’t modify or replace any WordPress files or functions.</p>
<h4>Home and GitHub</h4>
<ul>
<li>Learn more about the plugin: <a href="https://www.dev4press.com/plugins/debugpress/" rel="nofollow ugc">DebugPress Website</a></li>
<li>Contribute to plugin development: <a href="https://github.com/dev4press/debugpress" rel="nofollow ugc">DebugPress on GitHub</a></li>
</ul>
<h4>Quick Overview Video</h4>
<p><span class="embed-youtube" style="text-align:center; display: block;"><iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/-eFnBRLhy-s?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe></span></p>
<h4>Pretty Print for objects</h4>
<p>To display the content of objects or arrays, plugin has pretty print functionality through use of simpler PrettyPrint library, or more robust third-party library Kint. You can choose one or the other from the plugin Settings, Advanced tab.</p>
<h4>Debugger Panels</h4>
<p>Currently, the plugin has the following panels:</p>
<ul>
<li>Basic</li>
<li>Request (optional)</li>
<li>Query (for frontend only)</li>
<li>Content (optional)</li>
<li>Roles (optional)</li>
<li>Constants (optional)</li>
<li>Hooks (optional)</li>
<li>PHP (optional)</li>
<li>Server (optional)</li>
<li>Enqueue (optional)</li>
<li>SQL Queries (if SQL queries logging is enabled)</li>
<li>User (optional, if user is logged in only)</li>
<li>HTTP (optional, if HTTP API calls are captured)</li>
<li>bbPress (optional, on bbPress forum pages only)</li>
<li>Plugins (optional, if plugins store data)</li>
<li>Errors (for all captured PHP errors)</li>
<li>Doing It Wrong (for captured WordPress Doing It Wrong warnings)</li>
<li>Deprecated (for captured PHP deprecated warnings)</li>
<li>AJAX (for captured AJAX calls while page is active)</li>
<li>Store (for any user stored objects during the page loading)</li>
<li>Tools (internal and external tools links)</li>
<li>Debug Log (load content on demand from WordPress ‘debug.log’)</li>
<li>Layout (control the size, position and activation of the popup)</li>
</ul>
<h4>SQL Queries</h4>
<p>This panel lists all the queries WordPress has run. It allows you to order the queries by execution order or length of execution, and all queries can be filtered by the query type, database table it targets or the WordPress function that called it. Every query displays the execution time, order, caller functions stack and fully formatted SQL query that is easy to read. For some Dev4Press created plugins (and that list will grow), DebugPress can detect the source of the query and allow you to filter by the plugin calling the query.</p>
<h4>PHP and WordPress Errors</h4>
<p>Plugin has 3 panels dedicated to showing PHP and WordPress errors and warnings. The Plugin captures this information during the page load, and it shows full debug trace as returned by the PHP debug tracing function.</p>
<h4>AJAX</h4>
<p>The plugin tracks every AJAX call coming through WordPress <code>admin-ajax.php</code> handler, and with every response, it returns HTTP headers with AJAX request basic execution information. Right now, plugin is not returning a list of logged errors or SQL queries, because both can produce huge output that goes over the HTTP header limits. Plan is to introduce these in the future plugin versions.</p>
<h4>Info Panels</h4>
<p>In the administration Tools menu, plugin adds DebugPress Info page showing several panels</p>
<ul>
<li>PHP Info: full formatted results from <code>phpinfo()</code> function</li>
<li>OPCache Info: full settings and statistics for the OPCache PHP extension</li>
<li>MySQL Variables: full MySQL settings retrieved from the database</li>
</ul>
<h4>Plugin Settings</h4>
<p>The plugin has various options controlling the plugin activation, button integration position, user roles that can see the debugger window, options to attempt overriding WordPress debug flags and options controlling the visibility of optional debugger panels.</p>
<h4>Log into Database</h4>
<p>Debugger popup is visible for the request running in the browser. But there are many requests that are happening in the background (AJAX calls, REST API calls…), and for them, you can’t see errors, call information and other stuff in the debugger. Because of that, DebugPress supports logging of various events into database with the use of ‘coreActivity’ plugin, and it is highly recommended to install and use coreActivity.</p>
<p>Log various debug events into a database with the free plugin: <a href="https://wordpress.org/plugins/coreactivity/" rel="ugc">coreActivity Plugin</a>, supporting over 120 events and 10 popular WordPress plugins. DebugPress related events will be logged and available for later analysis, and this includes errors, AJAX calls, and HTTP API calls.</p>
<h4>Documentation and Support</h4>
<p>To get help with the plugin, you can use WordPress.org support forums, or you can use Dev4Press.com support forums.</p>
<ul>
<li>Plugin Documentation: <a href="https://www.dev4press.com/kb/product/debugpress/" rel="nofollow ugc">DebugPress Website</a></li>
<li>Support Forum: <a href="https://support.dev4press.com/forums/forum/plugins-free/debugpress/" rel="nofollow ugc">Dev4Press Support</a></li>
</ul>


DebugPress: Debugger in Popup

Great plugin for developers. Thank you for building and sharing this with the community.

Excellent

Easy-to-use plugin for debugging and profiling website loading, SQL queries analysis, help with development, bug fixing, all in configurable popup.

Query Monitor vs DebugPress: Debugger in Popup