Home

Awesome

<img src=".wordpress-org/icon-256x256.png" align="right" width="100" height="100" alt="">

WordPress Plugin Version License WordPress Tested Build Status

Query Monitor

Query Monitor is the developer tools panel for WordPress. It enables debugging of database queries, PHP errors, hooks and actions, block editor blocks, enqueued scripts and stylesheets, HTTP API calls, and more.

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.

Query Monitor focuses heavily on presenting its information in a useful manner. Here's an example showing aggregate database queries grouped by the components responsible for them:

Aggregate Database Queries by Component

Features

Database Queries

Filtering queries by component or calling function makes it easy to see which plugins, themes, or functions on your site are making the most (or the slowest) database queries.

Hooks & Actions

Theme

PHP Errors

Doing it Wrong

Block Content

Request

Scripts & Styles

Languages

HTTP API Requests

User Capability Checks

Multisite

Redirects

Ajax

The response from any jQuery Ajax request on the page will contain various debugging information in its headers. Any errors also get output to the developer console. No hooking required.

Currently this includes PHP errors and some overview information such as memory usage, but this will be built upon in future versions.

REST API

The response from an authenticated WordPress REST API request will contain various debugging information in its headers, as long as the authenticated user has permission to view Query Monitor's output.

Read more about debugging REST API requests with Query Monitor.

Admin Screen

Environment Information

Logging

Debugging messages can be sent to the Logs panel using actions. This works as a good replacement for var_dump():

do_action( 'qm/debug', 'This happened!' );

The logger is PSR-3 compatible, so you can use any of the following actions which correspond to PSR-3 log levels:

A log level of warning or higher will trigger a notification in Query Monitor's admin toolbar.

Read more about profiling and logging in Query Monitor.

Profiling

Basic performance profiling can be displayed in the Timings panel using actions in your code:

// Start the 'foo' timer:
do_action( 'qm/start', 'foo' );

// Run some code
my_potentially_slow_function();

// Stop the 'foo' timer:
do_action( 'qm/stop', 'foo' );

Read more about profiling and logging in Query Monitor.

Everything Else

Authentication

By default, Query Monitor's output is only shown to Administrators on single-site installations, and Super Admins on Multisite installations.

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 when you're logged in as a user who cannot usually see Query Monitor's output. See the Settings panel for details.

Notes

A Note on Query Monitor's Implementation

In order to do a few clever things, Query Monitor symlinks a custom db.php into your WP_CONTENT_DIR which means it loads very early. This file gets included before the database driver is loaded, meaning this portion of Query Monitor loads before WordPress even engages its brain.

In this file is Query Monitor's extension to the wpdb class which:

If your WP_CONTENT_DIR isn't writable and therefore the symlink for db.php can't be put in place, Query Monitor still functions, but this extended functionality won't be available. You can manually create the db.php symlink if you have permission.

Screenshots

Admin Toolbar Menu

Admin Toolbar Menu

Database Queries

Database Queries

Capability Checks

Capability Checks

Aggregate Database Queries by Component

Aggregate Database Queries by Component

Aggregate Database Queries by Calling Function

Aggregate Database Queries by Calling Function

Hooks and Actions

Hooks and Actions

HTTP API Requests

HTTP API Requests

Frequently Asked Questions

Does this plugin work with PHP 8?

Yes, it's actively tested and working up to PHP 8.2.

Who can see Query Monitor's output?

By default, Query Monitor's output is only shown to Administrators on single-site installations, and Super Admins on Multisite installations.

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 when you're logged in as a user who cannot usually see Query Monitor's output. See the Settings panel for details.

Does Query Monitor itself impact the page generation time or memory usage?

Short answer: Yes, but only a little.

Long answer: Query Monitor has a small impact on page generation time because it hooks into a few places in WordPress in the same way that other plugins do. The impact is negligible.

On pages that have an especially high number of database queries (in the hundreds), Query Monitor currently uses more memory than I would like it to. This is due to the amount of data that is captured in the stack trace for each query. I have been and will be working to continually reduce this.

Can I prevent Query Monitor from collecting data during long-running requests?

Yes, you can call do_action( 'qm/cease' ) to instruct Query Monitor to cease operating for the remainder of the page generation. It will detach itself from further data collection, discard any data it's collected so far, and skip the output of its information.

This is useful for long-running operations that perform a very high number of database queries, consume a lot of memory, or otherwise are of no concern to Query Monitor, for example:

Are there any add-on plugins for Query Monitor?

A list of add-on plugins for Query Monitor can be found here.

In addition, Query Monitor transparently supports add-ons for the Debug Bar plugin. If you have any Debug Bar add-ons installed, deactivate Debug Bar and the add-ons will show up in Query Monitor's menu.

Where can I suggest a new feature or report a bug?

Please use the issue tracker on Query Monitor's GitHub repo as it's easier to keep track of issues there, rather than on the wordpress.org support forums.

Is Query Monitor available on Altis?

Yes, the Altis Developer Tools are built on top of Query Monitor.

Is Query Monitor available on WordPress VIP?

Yes, but a user needs to be granted the view_query_monitor capability to see Query Monitor even if they're an administrator. See the WordPress VIP documentation for more details.

I'm using multiple instances of wpdb. How do I get my additional instances to show up in Query Monitor?

This feature was removed in version 3.12 as it was rarely used and considerably increased the maintenance burden of Query Monitor itself. Feel free to continue using version 3.11 if you need to make use of this feature.

Can I click on stack traces to open the file in my editor?

Yes. You can enable this on the Settings panel.

How can I report a security bug?

You can report security bugs through the official Query Monitor Vulnerability Disclosure Program on Patchstack. The Patchstack team helps validate, triage, and handle any security vulnerabilities.

Do you accept donations?

I am accepting sponsorships via the GitHub Sponsors program. If you work at an agency that develops with WordPress, ask your company to provide sponsorship in order to invest in its supply chain. The tools that I maintain probably save your company time and money, and GitHub sponsorship can now be done at the organisation level.

In addition, if you like the plugin then I'd love for you to leave a review. Tell all your friends about it too!

Privacy Statement

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.

Query Monitor's full privacy statement can be found here.

Accessibility Statement

Query Monitor aims to be fully accessible to all of its users. It implements best practices for web accessibility, outputs semantic and structured markup, uses the accessibility APIs provided by WordPress and web browsers where appropriate, and is fully accessible via keyboard.

That said, Query Monitor does not conform to the Web Content Accessibility Guidelines (WCAG) 2.0 at level AA like WordPress itself does. The main issue is that the user interface uses small font sizes to maintain a high information density for sighted users. Users with poor vision or poor motor skills may struggle to view or interact with some areas of Query Monitor because of this. This is something which I'm acutely aware of and which I work to gradually improve, but the underlying issue of small font sizes remains.

If you've experienced or identified another accessibility issue in Query Monitor, please open a thread in the Query Monitor plugin support forum and I'll try my best to address it swiftly.

Related Tools

Debugging is rarely done with just one tool. Along with Query Monitor you should be aware of other plugins and tools for debugging and profiling your website. Here are some recommendations:

WordPress Plugins

Query Monitor also has several add-on plugins which extend its functionality, and transparently supports add-ons for the Debug Bar plugin (see the FAQ for more info).

See also my list of WordPress Developer Plugins.

Other tools

Hosted services

Contributing

Code contributions, feedback, and feature suggestions are very welcome. See CONTRIBUTING.md for more details.

Icon

Query Monitor's icon was designed by Tubagus Didin Asrori.

License: GPLv2

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 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.