500 Internal Server Error in WordPress: Troubleshooting Guide

A 500 Internal Server Error in WordPress is a server-side failure that stops your site from loading due to misconfiguration, faulty code, or resource limits. Common causes include a corrupted .htaccess file, plugin or theme conflicts, PHP memory or timeout limits, and server permission errors. Fix it by enabling debugging, reviewing logs, and isolating conflicts.

If you’re seeing a 500 Internal Server Error in WordPress, don’t panic. This guide shows you exactly how to diagnose and fix the WordPress 500 error step-by-step using proven methods I use daily as a hosting and WordPress specialist. We’ll cover fast fixes, deeper server-level checks, and prevention so it doesn’t come back.

What Is a 500 Internal Server Error in WordPress?

The 500 error is a generic HTTP status code that indicates the server couldn’t fulfill the request. In WordPress, it usually stems from a bad .htaccess rule, a plugin/theme conflict, exhausted PHP memory, a faulty update, file permission issues, or a misconfigured PHP/Apache/Nginx stack. Because it’s server-side, you won’t see a precise error in the browser without enabling debug or checking logs.

Common Causes of the WordPress 500 Error

• Corrupted or incompatible .htaccess rewrite rules
• Plugin or theme conflicts, especially after updates
• Insufficient PHP memory or timeouts (e.g., heavy imports, backup/optimizer plugins)
• Incorrect file permissions/ownership
• PHP version incompatibility or missing PHP extensions
• Opcode/page caching issues (OPcache, object cache, server cache, CDN conflicts)
• Database corruption or overloaded queries
• Web server or PHP-FPM misconfiguration and resource exhaustion
• Security/WAF/ModSecurity false positives blocking requests
• Malware or injected code causing fatal errors

Quick Checks Before Deep Debugging

• Confirm the 500 error appears site-wide (frontend and /wp-admin) or only on specific URLs.
• Temporarily disable CDN/WAF (e.g., pause Cloudflare) and clear all caches.
• Note the time of the error and any recent changes: plugin/theme/core updates, new code, migrations.
• Ensure you have a working backup or snapshot (ideal: restore to staging for safe testing).
• Open server and WordPress logs; they are your fastest route to the root cause.

Step-by-Step Fixes for 500 Internal Server Error in WordPress

1) Enable WordPress Debugging and Review Logs

Turn on debug to capture PHP errors and stack traces. Edit wp-config.php (above the “That’s all…” line):

define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
@ini_set('display_errors', 0);

Reproduce the error, then check /wp-content/debug.log. Also review your server error log (e.g., error_log in the site root or via cPanel/hosting panel). The last entries usually point to the faulty plugin, theme file, or memory limit.

2) Reset and Regenerate Your .htaccess File (Apache/LiteSpeed)

A corrupted or overly complex .htaccess is a top cause of 500 errors. Via FTP or File Manager:

• Rename .htaccess to .htaccess.bak.
• Try loading the site; if it works, regenerate permalinks in WordPress: Settings > Permalinks > Save.

Default WordPress .htaccess for pretty permalinks (Apache/LiteSpeed):

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

3) Increase PHP Memory Limit and Execution Time

Low memory or strict timeouts frequently trigger 500s under load. In wp-config.php add:

define('WP_MEMORY_LIMIT', '256M');
define('WP_MAX_MEMORY_LIMIT', '512M');

If your host allows php.ini or .user.ini overrides:

memory_limit = 512M
max_execution_time = 120
max_input_vars = 5000
post_max_size = 64M
upload_max_filesize = 64M

After changes, clear OPcache or restart PHP-FPM if you have access. Re-test the site.

4) Deactivate All Plugins and Switch to a Default Theme

Most 500 errors are plugin-related. If you can’t access wp-admin, rename the wp-content/plugins folder to plugins.disabled. To pinpoint the culprit, restore the folder and deactivate/reactivate plugins one by one.

With WP-CLI:

wp plugin deactivate --all
wp theme activate twentytwentyfour

Re-enable plugins in batches to identify conflicts. Pay special attention to security, caching, backup, and page builder plugins after updates or migrations.

5) Fix File Permissions and Ownership

Incorrect permissions can block PHP from reading or executing files, causing 500s. On Linux servers, recommended values are 644 for files and 755 for directories:

find /path/to/wordpress/ -type d -exec chmod 755 {} \;
find /path/to/wordpress/ -type f -exec chmod 644 {} \;

Ownership should match the web user (often www-data, nobody, or your account). Your hosting support can correct this safely.

6) Verify PHP Version and Extensions

Using an incompatible PHP version or missing extensions can break themes/plugins. WordPress runs best on PHP 8.1 or 8.2. In your hosting panel’s PHP Selector, confirm:

• Version: PHP 8.1/8.2 (unless a legacy plugin requires older)
• Extensions: curl, mbstring, json, mysqli, openssl, zip, intl, xml, gd
• Disable outdated loaders (e.g., old ionCube) if not needed.

After switching versions, purge OPcache and retest.

7) Clear All Caches: Plugin, Server, and CDN

Stale or corrupted caches can surface as 500s. Clear caches from your caching plugin, hosting panel (OPcache/object cache), and CDN (full purge). Temporarily disable security rules (e.g., ModSecurity) if logs show false positives.

8) Repair and Optimize the Database

Corrupted tables or heavy autoloaded options can cause fatal errors. Enable repair temporarily in wp-config.php:

define('WP_ALLOW_REPAIR', true);

Visit https://example.com/wp-admin/maint/repair.php to repair/optimize. Remove the constant afterward. With WP-CLI:

wp db repair
wp transient delete --all
wp option list --search=autoload=yes --fields=option_name,size --format=table

If an option (e.g., from a plugin) has huge autoload size, fix or remove it carefully (backup first).

9) Nginx/Reverse Proxy and PHP-FPM Checks

On Nginx, ensure WordPress rewrites and PHP-FPM upstream are correct. Typical config snippet:

location / {
    try_files $uri $uri/ /index.php?$args;
}
location ~ \.php$ {
    include fastcgi_params;
    fastcgi_pass unix:/run/php/php8.2-fpm.sock;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    fastcgi_read_timeout 120;
}

If PHP-FPM hits limits (pm.max_children, memory), you’ll see 500s under traffic spikes. Your host can tune pools or increase resources.

10) Scan for Malware or Suspicious Code

If the error appeared without changes, scan with a reputable security plugin and compare core files to WordPress originals. Look for unfamiliar PHP files in wp-content/uploads and strange .htaccess rules. Clean or restore from a known-good backup.

How to Read Error Logs Effectively

• PHP Fatal error: Often points to the exact plugin/function. Fix by updating or disabling the component.
• Allowed memory size exhausted: Increase memory and investigate heavy queries or plugins.
• Premature end of script headers: Common with timeouts or misconfigured fastcgi/PHP-FPM.
• Rewrite or permission denied: Inspect .htaccess and file permissions.
• ModSecurity triggered: Whitelist the rule ID or ask your host to adjust.

Preventing Future 500 Errors

• Use staging for updates and test major plugin/theme changes before going live.
• Keep WordPress core, themes, and plugins updated and remove unused plugins.
• Monitor PHP error logs and set alerts for spikes or fatal errors.
• Right-size your hosting resources; heavy WooCommerce or LMS sites need more PHP workers and memory.
• Implement regular backups (daily + on-demand) and verify restorations.
• Optimize your database and limit autoloaded options growth.
• Use compatible PHP versions and supported extensions; avoid outdated loaders.

When to Contact Your Host (and How YouStable Helps)

Reach out to hosting support if logs show server-level limits, you can’t access logs, or the 500 error persists after isolating plugins/themes. Provide exact timestamps, recent changes, and affected URLs to speed resolution.

At YouStable, our WordPress-optimized hosting includes real-time PHP error logging, WP-CLI, staging, one-click PHP version selector, automatic backups, LiteSpeed caching, and ModSecurity tuning. If a 500 error hits, our 24/7 engineers can inspect logs, adjust PHP-FPM, and help pinpoint the exact plugin/theme or server rule causing the failure—so you recover faster and stay stable.

Troubleshooting Checklist (TL;DR)

• Enable WP_DEBUG_LOG and check server error logs
• Reset .htaccess and regenerate permalinks
• Increase PHP memory/timeouts
• Disable all plugins; switch to a default theme
• Fix permissions (755/644) and verify ownership
• Confirm PHP version and required extensions
• Clear plugin/server/CDN caches and review WAF rules
• Repair database and remove bloated autoloaded options
• Review Nginx/Apache and PHP-FPM settings; check resource limits
• Scan for malware; restore clean backups if needed

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