Query Monitor
Plugin Review
AI-ResearchedWhat is Query Monitor?
Query Monitor is a developer tools panel that sits inside your WordPress admin toolbar. Created by John Blackbourn, it has been actively maintained for 13 years. The plugin currently holds 200,000+ active installs with a 4.9 out of 5 rating from 467 reviews. An impressive 97% of those ratings are five-star, indicating strong user satisfaction. It provides real-time debugging data for database queries, PHP errors, hooks, HTTP API calls, and block editor blocks. The plugin supports WordPress versions up to three years old and PHP 7.4 or higher, with active testing up to PHP 8.5.
Query Monitor focuses on presenting complex debugging information in a useful way. For example, it groups database queries by the plugin or theme that triggered them. This makes it easier to identify which component is causing a performance bottleneck. Version 4.0.6 was last updated on April 11, 2026, and the plugin is tested up to WordPress 6.9.4.
Key Features of Query Monitor
- Database Query Analysis — Shows all database queries with notifications for slow, duplicate, or erroneous queries, plus filtering by query type and responsible component.
- PHP Error Display — Presents PHP errors with their responsible component and call stack, plus a visible warning in the admin toolbar.
- Block Editor & FSE Support — Displays blocks and their properties within post content and full site editing environments.
- Script & Stylesheet Debugging — Lists enqueued scripts and stylesheets with dependencies, dependents, and alerts for broken dependencies.
- HTTP API Request Tracking — Shows each HTTP request with response code, responsible component, and time taken, plus alerts for failed requests.
- User Capability Check Logging — Records every user capability check along with the result and any parameters passed to the check.
- Redirect Call Stack Headers — Adds an HTTP header with the call stack whenever a redirect occurs, usable with browser developer tools.
- Ajax & REST API Debugging — Captures debugging data from jQuery-initiated Ajax requests and REST API calls on the page.
Who Should Use Query Monitor?
Query Monitor is built for WordPress developers and advanced site builders. If you write custom themes or plugins, you will find immediate value in tracing database query origins and PHP error sources. The plugin also suits site owners managing complex WooCommerce stores or membership sites where performance matters. With 200,000+ installs, it has become a standard tool in the WordPress development community.
A beginner site owner may find the interface overwhelming at first. However, the admin toolbar menu provides an overview summary that is accessible to intermediate users. The plugin only displays output to Administrators on single-site installs and Super Admins on Multisite. You can also set an authentication cookie to view output when logged out or as a non-admin user. The 27% support resolution rate suggests the community handles most questions through forums or the plugin website.
Installation & Setup
Install Query Monitor like any other plugin from the WordPress repository. After activation, you will see a new admin toolbar item with a summary of the current page load. No configuration is required to start seeing database queries, PHP errors, and enqueued assets. Advanced users can explore the Settings panel to set an authentication cookie for logged-out viewing.
Support & Community
Support is managed through the WordPress plugin forum. Over the past two months, there were 11 open threads and 3 resolved threads, giving a 27% resolution rate. This figure is lower than average for well-established plugins, but the high rating of 4.9 from 467 ratings suggests that most users find the plugin works reliably out of the box. The 2% one-star ratings likely reflect edge cases or conflicts with specific server configurations. John Blackbourn maintains a dedicated plugin website with complete documentation for those needing deeper guidance.
Pros & Cons
- Rated 4.9/5 from 467 reviews with 97% 5-star ratings, indicating exceptional user satisfaction among developers.
- Shows aggregate database queries grouped by responsible plugin or theme, enabling quick identification of performance bottlenecks.
- Supports debugging of Ajax calls, REST API calls, and user capability checks, covering advanced development scenarios beyond basic page loads.
- Highlights slow, duplicate, or erroneous queries and deprecated functionality, helping prevent common performance and code quality issues.
- Works with block themes and full site editing, and supports WordPress versions up to three years old, ensuring broad compatibility.
- Only 3 of 11 support threads are resolved (27% rate), suggesting limited developer support for troubleshooting issues.
- Requires PHP 7.4 or higher, excluding sites on older PHP versions that are still common in legacy environments.
- The admin toolbar panel can add visual clutter on the front end for non-developer users, requiring manual disabling or role-based access.
- Provides no built-in way to export or log debugging data over time, limiting its use for long-term performance monitoring.
Technical Details
- Requires WordPress
- 6.1+
- Requires PHP
- 7.4+
- Tested up to WP
- 6.9.4
- First Released
- 2013 (13+ years)
- Support (last 2 months)
- 11 threads — 27% resolved
Feature Tags
Frequently Asked Questions
Yes, Query Monitor is completely free and available on WordPress.org. It has been free since its first release in 2013.
Query Monitor has over 200,000 active installations. It also holds a near-perfect rating of 4.9 out of 5 from 467 user ratings.
Query Monitor requires WordPress 6.1 or higher. It is tested up to WordPress 6.9.4 and supports versions up to three years old.
Yes, the plugin was last updated on April 11, 2026, and is actively maintained by its author, John Blackbourn. It is tested with PHP up to version 8.5.
Query Monitor requires PHP version 7.4 or higher. It works with modern PHP versions, including PHP 8.5.
Support threads are handled on WordPress.org, with 11 threads in the last 2 months and a 27% resolution rate. Most users find the plugin stable and well-documented.
It is primarily a developer tool, but beginners can benefit from its clear admin toolbar overview. By default, its output is only shown to Administrators, so it stays out of the way until you need it.
It shows database queries with slow or duplicate query notifications, PHP errors, hooks and actions, enqueued scripts, and HTTP API calls. You can filter output by plugin or theme to identify performance issues, and it supports debugging of Ajax and REST API calls.