6 Best WordPress Developer Plugins (2026): Free Tools We Tested
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Short answer: The six free WordPress developer plugins we would install first are Query Monitor (find slow queries and PHP errors), Code Snippets (add PHP without touching functions.php), WP Crontrol (see and run scheduled tasks), Redirection (301 redirects and 404 logs), User Switching (test as any user) and Health Check & Troubleshooting (debug plugin conflicts safely). All six were light in our test, adding between 0 and 1 MB of memory. Health Check has not been updated since July 2024, so use it with care.
WordPress developer plugins are the toolbox you reach for when something breaks or when you need to change how a site behaves without editing theme files. They are useful for developers, but also for site owners who want to understand why a page is slow or why an email did not go out.
We installed the six most useful free WordPress developer plugins on a clean WordPress 7.1.3 site, one at a time, and measured what each adds to the site. A good debugging tool should not become the problem you are debugging, and none of these did.
Our picks at a glance
1
Query MonitorFind slow queries, hooks and PHP errors
9.6/10
2
Code SnippetsAdd PHP snippets safely
9.7/10
3
WP CrontrolSee and control WP-Cron
9.7/10
4
RedirectionRedirects and 404 monitoring
9.5/10
5
User SwitchingTest the site as any user
9.9/10
6
Health Check & TroubleshootingTroubleshoot plugin conflicts
8.7/10
The order reflects what we would recommend for most sites, weighing features and hosting fit. The score measures only what each plugin costs your site.
WordPress developer plugins compared: our test results
None of these developer plugins added CSS or JavaScript for logged-out visitors. Lower memory is better.
| Measurement | Query Monitor | Code Snippets | WP Crontrol | Redirection | User Switching | Health Check & Troubleshooting |
|---|---|---|---|---|---|---|
| Version tested | 4.0.7 | 4.0.0 | 2.0.0 | 5.10.1 | 1.12.2 | 1.7.1 |
| Active installs | 200,000+ | 1 million+ | 300,000+ | 2 million+ | 200,000+ | 200,000+ |
| WordPress.org rating | 4.9 (470) | 4.7 (509) | 4.4 (167) | 4.4 (703) | 4.9 (238) | 3.6 (181) |
| CSS/JS added for visitors | 0 KB | 0 KB | 0 KB | 0 KB | 0 KB | 0 KB |
| Extra PHP memory | 1.0 MB | 0.8 MB | 0.8 MB | 0.7 MB | 0.0 MB | 0.0 MB |
| Database tables | 0 | 1 | 0 | 0 | 0 | 0 |
| Memory in the admin | 2.5 MB | 2.4 MB | 1.4 MB | 1.4 MB | 0.1 MB | 0.0 MB |
| Last updated | 2026-06-20 | 2026-10-21 | 2026-10-15 | 2026-09-19 | 2026-08-29 | 2024-07-25 |
| Tested up to WordPress | 7.0.7 | 7.1.3 | 7.1.3 | 7.1.3 | 7.1.3 | 6.6.10 |
| Notices / redirects | None | None | None | setup notice | None | None |
| Plugin size | 0.6 MB | 4.1 MB | 0.8 MB | 1.6 MB | 0.1 MB | 0.4 MB |
| WPGlory score | 9.6/10 | 9.7/10 | 9.7/10 | 9.5/10 | 9.9/10 | 8.7/10 |
The front-end cost of every developer plugin here was tiny: 1 MB or less of memory, at most one table. The biggest difference is maintenance. Five of the six were updated in the last five months; Health Check & Troubleshooting was last updated on 25 July 2024 and is only tested up to WordPress 6.6, which pulls its score down.
1. Query Monitor: the first of the WordPress developer plugins to install
9.6/10 Free plan v4.0.7 · 200,000+ installs · 4.9★ on WordPress.org
Query Monitor is the developer tools panel for WordPress. It shows every database query on a page, which plugin or theme ran it and how long it took, plus PHP errors, hooks, HTTP API calls, scripts and styles, and more. When a page is slow, it usually tells you why within a minute.
It only shows its panel to administrators, through an item in the admin bar, and it has no admin menu at all. In our test it added 1.0 MB of memory on the front end and 2.5 MB in the admin, no tables and one cron job. It has a 4.9-star rating. Its listing says it is tested up to WordPress 7.0.7, one minor version behind the current release, and it worked normally on 7.1.3.
Tip: install it when you need it and deactivate it when you are done, especially on busy sites. Like most developer plugins, it is a diagnostic tool, not something visitors need.
Pros
- Shows slow queries, errors and hooks per page
- Visible only to admins, no menu clutter
- Light: 1 MB, no tables
Cons
- Lots of data; takes time to learn
- Best switched off when not debugging
2. Code Snippets: add PHP without editing theme files
9.7/10 Free plan v4.0.0 · 1 million+ installs · 4.7★ on WordPress.org
Code Snippets, one of the most installed developer plugins, gives you a safe place for the small PHP changes that tutorials tell you to paste into functions.php. Each snippet can be switched on or off, has a title and description, and survives theme updates and theme changes.
It added 0.8 MB of memory, one database table (where your snippets live), and a Snippets menu with 7 items. If a snippet causes a fatal error, the plugin can catch common mistakes before they take the site down, but keep a backup anyway. Of all the WordPress developer plugins here, it is the one most site owners end up using every week.
Pros
- Snippets survive theme changes
- Turn snippets on and off without FTP
- Light: 0.8 MB
Cons
- A bad snippet can still break a site
- One more place where site logic lives
3. WP Crontrol: see and control WP-Cron
9.7/10 Free plan v2.0.0 · 300,000+ installs · 4.4★ on WordPress.org
WordPress runs scheduled tasks (publishing scheduled posts, sending emails, running backups) through WP-Cron. WP Crontrol lists every scheduled event, shows when it will run next and which hook it calls, and lets you run, pause, edit or delete events.
It is how we checked the cron jobs in all our plugin tests: for example, Kadence Security added 8 scheduled events and Wordfence 6. It added 0.8 MB of memory, no tables and two small menu items under Tools and Settings. Few WordPress developer plugins answer the question “why did that not run?” as quickly.
Pros
- Explains missed scheduled posts and stuck backups
- Run any event on demand
- Light: 0.8 MB, no tables
Cons
- Deleting the wrong event can break a plugin
4. Redirection: redirects and 404 monitoring
9.5/10 Free plan v5.10.1 · 2 million+ installs · 4.4★ on WordPress.org
Redirection manages 301 redirects, logs 404 errors so you can fix broken links, and can redirect based on conditions such as login status. It has more than 2 million active installs, the most of the developer plugins we tested.
It added 0.7 MB of memory and showed a notice on the dashboard and Plugins page asking us to finish its setup. That is because it creates its database tables only when you complete the setup wizard, which is a sensible choice. If you already use Rank Math, its Redirections module covers the basics, so you may not need both.
Pros
- Easy 301 redirects and 404 log
- Creates tables only when you finish setup
- Light: 0.7 MB
Cons
- Setup notice until you run the wizard
- Overlaps with SEO plugins that include redirects
5. User Switching: test the site as any user
9.9/10 Free plan v1.12.2 · 200,000+ installs · 4.9★ on WordPress.org
User Switching is one of the simplest developer plugins: it adds a “Switch To” link on the Users screen. One click and you see the site exactly as that user does, then you switch back. It is perfect for testing membership levels, shop customer accounts and editor permissions.
It was the lightest of the developer plugins in this test: no measurable front-end memory, 0.1 MB in the admin, no tables, no options and no menu. It has a 4.9-star rating.
Pros
- Instant switch between users and back
- Practically no overhead
- No settings to configure
Cons
- Admins only; be careful on live sites with customer data
6. Health Check & Troubleshooting: troubleshoot plugin conflicts (with a caveat)
8.7/10 Free plan v1.7.1 · 200,000+ installs · 3.6★ on WordPress.org
Health Check & Troubleshooting has a unique feature: Troubleshooting Mode. It disables all plugins and switches to a default theme for your session only, while visitors keep seeing the normal site. You then turn plugins back on one by one to find the one causing a problem, without taking the live site down.
It added nothing measurable in our test. But it was last updated in July 2024 and is only tested up to WordPress 6.6. The core Site Health screen (Tools, Site Health) already covers the health checks, so install this plugin only when you need Troubleshooting Mode, and remove it afterwards, as you would with any outdated developer plugin.
Pros
- Troubleshooting Mode: test conflicts without affecting visitors
- No measurable cost
Cons
- Not updated since July 2024
- Tested only up to WordPress 6.6
A simple debugging workflow with these plugins
Here is how these WordPress developer plugins fit together when something goes wrong:
- Something is slow: open the page with Query Monitor and sort queries by time or by component.
- A scheduled post or backup did not run: check WP Crontrol for missed or stuck events.
- Something broke after an update: use Troubleshooting Mode to find the plugin, on a staging copy if you can.
- A user reports a problem you cannot see: switch to their account with User Switching.
- You moved or renamed pages: add redirects and watch the 404 log in Redirection.
- You need a small code change: add it as a snippet in Code Snippets, with a clear title.
Keep WordPress developer plugins off when you do not need them
All six WordPress developer plugins in this test were light, but tools like Query Monitor and Health Check are diagnostic. Turn them on when you are investigating and off when you are done. Code Snippets, Redirection and User Switching can stay active because they do a job every day.
For more ways to keep a site fast, see our slow WordPress plugins guide, our WordPress cache plugins test and our backup plugins comparison.
How we tested
Every plugin was installed from WordPress.org on a clean WordPress 7.1.3 site (PHP 8.3, Kadence theme) in WordPress Playground on 26 October 2026. We activated one plugin at a time, measured the site, then deactivated it again, so each result is compared with the same clean baseline. We loaded the home page as a logged-out visitor three times and kept the median PHP peak memory, counted the CSS and JavaScript the plugin added, and recorded database tables, options, scheduled cron jobs, admin menus, notices, dashboard widgets and any redirect on the first admin visit. Ratings, installs and versions come from the WordPress.org plugin directory on the same day.
The WPGlory score rates what a plugin costs your site, not how many features it has: front-end weight 30%, server cost 20%, admin clutter 20%, WordPress.org rating 20% (weighted by the number of reviews) and maintenance 10%. Features are covered in the text. Read the full method.
FAQ
What is the most useful of these WordPress developer plugins?
Query Monitor. It shows what every page is doing (queries, errors, hooks and HTTP calls) and points you to the plugin or theme responsible.
Is it safe to use Code Snippets on a live site?
Yes, with care. Test snippets on staging first, give each one a clear name, and keep a backup. A wrong snippet can still cause errors.
Do WordPress developer plugins slow down a site?
The ones in this test added 1 MB of memory or less and nothing for visitors. Of these developer plugins, Query Monitor collects the most data for admins, so deactivate it when you are not debugging.
Is Health Check & Troubleshooting still safe to use?
It still worked in our test on WordPress 7.1.3, but it has not been updated since July 2024. Use it briefly for Troubleshooting Mode, then remove it.
Final verdict
Start with Query Monitor and Code Snippets
Of the WordPress developer plugins we tested, Query Monitor is the one that saves the most time, and Code Snippets is the safest way to add custom code. Add WP Crontrol, Redirection and User Switching as you need them; together they cover most of what WordPress developer plugins are for.
9.6/10
