The Complete Guide to WordPress Debugging Steps: From Zero to 100

WordPress is a powerful platform, but websites can still experience technical problems. Common issues include the White Screen of Death (WSOD), database connection errors, plugin conflicts, and performance problems.

Following the right WordPress debugging steps helps you identify the source of these issues and fix them systematically. This guide covers everything from enabling WP_DEBUG to checking plugins, themes, PHP settings, databases, REST API requests, and loopback connections.

Why WordPress Debugging Is Essential

WordPress websites depend on many components, including plugins, themes, PHP, databases, and server configurations. A problem with one component can affect the entire website.

Errors can also affect user experience and SEO. For example, PHP fatal errors can prevent search engines from properly accessing website content. Performance problems can also increase page load times.

Debugging is therefore more than finding a single bug. It helps maintain website stability, security, and performance.

Step 1: Activate the WordPress Debugging System

The first step is to activate WordPress’s built-in debugging system through the wp-config.php file.

This file is located in the root directory of your WordPress installation, usually inside public_html.

Access and Edit wp-config.php

You can access the file through an FTP client such as FileZilla or through your hosting control panel’s File Manager.

Follow these steps:

Open your website’s root directory.
Locate wp-config.php.
Open the file for editing.
Find the line /* That's all, stop editing! Happy blogging. */.
Add the following code immediately before it:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

These settings enable debugging while preventing errors from being displayed directly to visitors.

Understand the WP_DEBUG Constants

Each constant has a specific purpose:

WP_DEBUG: Enables WordPress debugging mode.
WP_DEBUG_LOG: Saves errors to a debug.log file.
WP_DEBUG_DISPLAY: Controls whether errors appear on the website.

Keeping WP_DEBUG_DISPLAY set to false is recommended on live websites. It prevents potentially sensitive technical information from being exposed publicly.

Advanced Debugging Options

Developers can enable additional debugging features when deeper investigation is necessary:

define( 'SCRIPT_DEBUG', true );
define( 'SAVEQUERIES', true );

SCRIPT_DEBUG forces WordPress to use development versions of its CSS and JavaScript files.

SAVEQUERIES records database queries for detailed analysis. Use it carefully because it can affect website performance.

Step 2: Analyze the debug.log File

Once WP_DEBUG_LOG is enabled, WordPress stores errors in the debug.log file inside the wp-content directory.

This file is one of the most useful tools for identifying the source of technical problems.

How to Read debug.log

Each error entry can provide several important details:

Error type: Such as Fatal Error, Warning, or Notice.
File path: Shows which plugin, theme, or WordPress file generated the error.
Line number: Identifies the specific line where the problem occurred.

Fatal errors are particularly important because they can stop PHP execution and cause serious problems such as the White Screen of Death.

For example, a path containing /wp-content/plugins/ can indicate that a plugin is responsible.

Step 3: Isolate Plugin and Theme Conflicts

Plugin and theme conflicts are among the most common causes of WordPress errors.

The best approach is to isolate the components systematically.

How to Troubleshoot the White Screen of Death

If the website shows a White Screen of Death and you cannot access the WordPress dashboard, use your hosting File Manager or FTP.

First, open:

wp-content

Then rename the plugins folder to something such as:

plugins_temp

This forces WordPress to deactivate the installed plugins.

Reload the website.

If it works again, a plugin is likely responsible.

Rename the folder back to plugins, then continue testing individual plugins.

Check for Theme Conflicts

If disabling the plugins does not solve the problem, check the active theme.

Open:

wp-content/themes

Then rename the active theme’s folder.

WordPress should automatically switch to an available default theme.

If the website works again, the original theme is likely causing the problem.

Find the Specific Plugin

If the plugins are responsible, return to the plugins folder.

Rename individual plugin folders one at a time. Check the website after each change.

When the problem disappears, you have identified the likely source.

You can then update the plugin, contact its developer, or replace it with a compatible alternative.

Step 4: Fix PHP Memory Limit Errors

A common WordPress error is:

“Allowed memory size of X bytes exhausted.”

This means a PHP process has attempted to use more memory than the server allows.

Resource-heavy plugins, themes, and complex websites can contribute to this problem.

Increase the WordPress Memory Limit

You can increase the WordPress memory limit through wp-config.php.

Add:

define( 'WP_MEMORY_LIMIT', '256M' );

A 256M limit is generally a reasonable minimum for modern WordPress websites.

You can also check the server’s php.ini file and update:

memory_limit = 256M

Some hosting providers impose their own limits. If these changes do not work, contact your hosting provider.

Step 5: Check WordPress Core Files and PHP Compatibility

Some critical errors result from corrupted WordPress files or incompatible PHP versions.

An interrupted WordPress update, for example, can leave core files incomplete.

Manually Update WordPress Core Files

If you cannot access the dashboard because of corrupted core files, you can perform a manual update.

Download the latest official WordPress package.
Keep your existing wp-content folder.
Keep your wp-config.php file.
Replace the other WordPress core files and folders.
Pay particular attention to directories such as wp-admin and wp-includes.

Always create a complete backup before replacing core files.

Check Your PHP Version

Modern WordPress websites should use a currently supported PHP version.

The original guide recommends PHP 8.1 or higher, with PHP 8.2+ as an ideal target.

You can check your current PHP environment through:

Tools > Site Health

If your PHP version is outdated, use your hosting control panel’s PHP Selector or contact your hosting provider.

Updating PHP can improve compatibility, security, and performance.

Step 6: Troubleshoot REST API and Loopback Problems

WordPress Site Health can identify infrastructure problems that affect the editor, plugins, updates, and other core features.

Two important checks involve the REST API and loopback requests.

Fix REST API Errors

The REST API allows WordPress components to communicate with the WordPress installation.

A REST API failure can affect the Gutenberg editor and many plugins.

Possible causes include:

Server firewalls
Cloud-based firewalls
Security plugins
Incorrect server configurations

If you use Cloudflare or another firewall, check whether internal requests are being blocked.

You can also temporarily deactivate security plugins to determine whether one of them is responsible.

Fix Loopback Request Failures

Loopback requests allow WordPress to send requests back to its own server.

They are used for scheduled tasks, updates, and other background processes.

A failed loopback request can result from:

DNS problems
Server configuration issues
PHP conflicts
Request timeouts
Limited server resources

Check that your domain resolves correctly from the server.

If the problem continues, ask your hosting provider to review the server error logs.

Step 7: Troubleshoot the Database and Permalinks

Database problems can cause critical errors, including:

“Error Establishing a Database Connection.”

Incorrect URLs or permalink configurations can also produce unexpected 404 errors.

Check Database Connection Details

Open wp-config.php and verify these values:

DB_NAME
DB_USER
DB_PASSWORD
DB_HOST

The DB_HOST value is usually localhost, although this can vary by hosting environment.

Make sure all database credentials match the information provided by your hosting provider.

Repair Database Tables

If you suspect corrupted database tables, WordPress provides a built-in repair utility.

Add this line to wp-config.php:

define('WP_ALLOW_REPAIR', true);

Then visit:

http://yourdomain.com/wp-admin/maint/repair.php

Run the available repair option.

Remove the WP_ALLOW_REPAIR line immediately after completing the repair.

Leaving it enabled can expose the repair tool publicly.

Rebuild WordPress Permalinks

If internal pages return 404 errors, the permalink structure may be corrupted.

If you can access the dashboard:

Go to Settings > Permalinks.
Do not change the existing structure.
Click Save Changes.

WordPress will refresh the permalink rules.

If you cannot access the dashboard, back up the .htaccess file and remove it through File Manager. After regaining access, save the permalink settings to regenerate it.

Conclusion: Keep Your WordPress Site Stable After Debugging

The right WordPress debugging steps can turn a confusing technical problem into a structured troubleshooting process.

Start by enabling WP_DEBUG and reviewing debug.log. Then isolate plugin and theme conflicts if necessary.

For resource-related errors, check PHP memory and your PHP version. You should also investigate REST API failures, loopback requests, database connections, and permalink problems.

Disable Debugging After Fixing the Problem

Do not leave debugging enabled permanently on a live website.

After completing the troubleshooting process, return these settings to false:

define( 'WP_DEBUG', false );
define( 'WP_DEBUG_LOG', false );
define( 'WP_DEBUG_DISPLAY', false );

Leaving debugging enabled can expose sensitive technical information and may affect website performance.

Regular maintenance, timely updates, reliable hosting, and proper monitoring can reduce recurring WordPress problems.

Frequently Asked Questions

What is WP_DEBUG in WordPress?

WP_DEBUG is a WordPress constant that activates the built-in debugging mode.

It helps identify PHP errors, warnings, and notices that may be causing problems on your website.

What should I do if my site shows the White Screen of Death?

First, enable WP_DEBUG_LOG and check the debug.log file.

If you cannot access the dashboard, use FTP or File Manager to rename the plugins folder. If that does not work, test the active theme in the same way.

How can I check whether a plugin is causing the problem?

Rename the wp-content/plugins folder to temporarily deactivate all plugins.

If the website recovers, rename the folder back and deactivate individual plugins one at a time until the problem returns.

What does the PHP memory exhausted error mean?

It means a PHP process has exceeded the memory limit assigned by the server.

You can usually increase the WordPress memory limit by adding WP_MEMORY_LIMIT to wp-config.php.

Why am I getting a REST API error?

A REST API error means WordPress cannot complete an internal API request.

Common causes include security plugins, firewalls, server configuration problems, and outdated PHP versions.

Is it safe to keep WP_DEBUG enabled permanently?

No.

Debugging can expose sensitive information about your website’s files and code.

After troubleshooting, set WP_DEBUG, WP_DEBUG_LOG, and WP_DEBUG_DISPLAY back to false.

How does PHP version compatibility affect WordPress?

Outdated PHP versions can cause compatibility problems and fatal errors with modern WordPress core, plugins, and themes.

Using a currently supported PHP release improves compatibility, security, and performance.

What are loopback requests in WordPress?

Loopback requests are internal requests that WordPress sends to itself.

They support scheduled tasks, updates, and certain health checks. Failures can indicate DNS, hosting, firewall, or PHP configuration problems.

Tagged article technology

The Complete Guide to WordPress Debugging Steps (From Zero to 100) and Fixing Common Errors