500 Internal Server Error — WordPress Diagnosis & Fix
Issue Type: Server-Level WordPress Error Symptom: Entire site returns HTTP 500 — no frontend, no wp-admin access Impact: Complete site outage, lost traffic, revenue disruption, SEO impact
Overview
The 500 Internal Server Error is one of the most disruptive WordPress failures a site owner can experience. Unlike page-level errors, a 500 takes down the entire website — including the WordPress admin dashboard — leaving no visible indication of the root cause. The generic error message provides no actionable information, making proper diagnosis essential.
Root Causes Diagnosed
Server Error Logs
The primary diagnostic source. Log entries reveal the specific script, file path, or module causing the server failure — for example, suexec permission errors, missing files, or fatal PHP exceptions.
Corrupted .htaccess File
A malformed or misconfigured .htaccess is among the most frequent 500 triggers. Renaming the file and regenerating it via WordPress Settings → Permalinks resolves this class of error reliably.
Incorrect File Permissions
WordPress requires specific permission levels: 644 for files, 755 for directories. Permissions set incorrectly — often following a server migration or hosting change — cause Apache and Nginx to reject script execution, resulting in a 500.
Plugin or Theme Conflict
A recently updated or installed plugin introducing a PHP fatal error will crash the entire WordPress application. Diagnosis requires deactivating all plugins via FTP (when wp-admin is inaccessible) and reactivating individually to isolate the offending component.
PHP Memory Exhaustion
WordPress reaching its allocated PHP memory limit terminates execution mid-request. Resolved by increasing the memory limit in wp-config.php or the server's php.ini configuration.
Resolution Approach
1. Pull and read server error logs to identify the specific failure point
2. Rename .htaccess and regenerate via WordPress if log points to rewrite rules
3. Audit and correct file/directory permissions via FTP or hosting file manager
4. Deactivate all plugins, confirm site restores, reactivate to isolate conflict
5. Increase PHP memory limit and verify stability under load
6. Document root cause and implement preventive measures