The key takeaway: most WordPress errors — white screen, 500 error, memory exhausted, 404s after a migration — trace back to one of four root causes: a plugin/theme conflict, a PHP memory or execution limit, a corrupted .htaccess file, or a database connection issue. Diagnosing which one is happening, rather than guessing at random fixes, gets a site back up fastest.
Why the Same Handful of Errors Keep Coming Back
WordPress runs on top of PHP, a web server, and a database, and most of the errors site owners run into are really failures in one of those three layers surfacing through WordPress rather than bugs in WordPress core itself. That's useful to know because it means the fix usually isn't "reinstall WordPress" — it's identifying which layer failed and addressing that specifically.
The four root causes below account for the large majority of WordPress errors reported in support forums and hosting tickets, and each has a specific, repeatable fix rather than a vague "try clearing your cache."
The White Screen of Death (WSOD)
A completely blank white page, with no error message visible, almost always means a PHP fatal error occurred but WordPress's default configuration hides errors from visitors rather than displaying them. The two most common triggers are a plugin or theme that isn't compatible with the site's current PHP version, and the site exhausting its allotted PHP memory limit mid-request.
To diagnose it: enable debug mode by adding two lines to wp-config.php — define('WP_DEBUG', true); and define('WP_DEBUG_LOG', true); — which writes the actual PHP error to a debug.log file inside wp-content instead of hiding it. This is documented in WordPress's own official debugging guide. Once the specific error and file are visible, the fix is usually deactivating the one plugin or theme named in the log.
If FTP or a file manager is the only access available (because the WSOD blocks the admin dashboard too), renaming the plugins folder inside wp-content forces every plugin to deactivate at once — the site should load again, and plugins can be reactivated one at a time to find the culprit.
500 Internal Server Error
Unlike the white screen, a 500 error is a generic server-level failure message, not a WordPress-specific one — it can come from a corrupted .htaccess file, a plugin conflict, a PHP execution timeout, or a server misconfiguration entirely unrelated to WordPress's own code. That's why checking the actual server error log (available in most hosting control panels) is a more reliable first step than guessing.
Common fixes, in order of how often they resolve it:
- Rename .htaccess temporarily (WordPress regenerates a default one when you resave Permalinks settings) — fixes corruption-related 500 errors immediately.
- Deactivate all plugins via phpMyAdmin by renaming the wp_options table's active_plugins row, if admin access is broken.
- Raise the PHP execution time limit if the error only happens on heavy operations like large imports.
"Allowed Memory Size Exhausted" Error
This specific, verbose PHP error ("Allowed memory size of X bytes exhausted") means a script tried to use more memory than PHP allows and is one of the more self-explanatory WordPress errors, since it names the exact problem in the message itself.
The fix has two levels. First, raise WordPress's own memory limit by adding define('WP_MEMORY_LIMIT', '256M'); to wp-config.php. Second, if that doesn't resolve it, the underlying PHP memory_limit set by the hosting environment itself may need raising too — WordPress's constant can't exceed what the server allows, so a host support ticket or a php.ini edit is sometimes unavoidable.
Quick Reference Table
| Error | Most Common Cause | First Fix to Try |
|---|---|---|
| White screen (WSOD) | Plugin/theme PHP fatal error | Enable WP_DEBUG, check debug.log |
| 500 Internal Server Error | Corrupted .htaccess or plugin conflict | Regenerate .htaccess via Permalinks |
| Memory exhausted | PHP memory limit too low | Raise WP_MEMORY_LIMIT in wp-config.php |
| 404 on all pages but homepage | Rewrite rules out of sync | Resave Permalinks settings |
| Database connection error | Wrong credentials or corrupted table | Verify wp-config.php DB credentials |
404 Errors After a Migration or Update
If the homepage loads but every other page returns a 404, the permalink structure stored in WordPress's database has fallen out of sync with the rewrite rules stored in .htaccess — a common side effect of moving hosts, restoring a backup, or switching servers. Resaving the Permalinks settings page in WordPress admin (Settings → Permalinks → Save Changes, with no actual changes needed) regenerates .htaccess and typically fixes this immediately.
Database Connection Errors
"Error establishing a database connection" means WordPress can't reach the MySQL/MariaDB database at all, which is distinct from the errors above since it happens before WordPress can even load enough to show its own error styling. The two most common causes are incorrect database credentials in wp-config.php (often after a migration) and a corrupted database table, most often wp_options. Verifying the DB_NAME, DB_USER, DB_PASSWORD, and DB_HOST constants in wp-config.php against the actual hosting panel resolves the credential case; a host-provided database repair tool usually resolves table corruption.
A Systematic Way to Diagnose Any WordPress Error
- Check the actual error, not just the symptom — enable WP_DEBUG or check the server error log rather than guessing from a blank screen or generic message.
- Test on a copy, not the live site, whenever the fix involves deactivating plugins or editing core files — a staging site exists exactly for this.
- Change one thing at a time — deactivating all plugins simultaneously tells you that a plugin is the cause, not which one.
- Rule out hosting-layer causes — PHP version mismatches and low memory limits are often a hosting configuration issue, not a WordPress one; see our broader WordPress speed and configuration guide for the hosting-layer factors that also affect error rates.
Preventing These Errors in the First Place
Poorly coded plugins — especially heavy image galleries or media-processing tools that load large libraries into memory on every request — are a disproportionately common source of memory-exhaustion crashes. A lighter-weight alternative that uses the server's own native image libraries instead of loading an external processing stack, like Erdo Image Optimizer, adds meaningfully less memory overhead than heavier all-in-one media plugins.
Beyond plugin choice, the same habits that prevent errors also make them faster to fix when they do happen: keeping regular backups, testing updates on a staging copy before pushing to production, and keeping PHP and WordPress core reasonably current so incompatibility errors don't compound with each passing year of neglect.
Common Mistakes When Fixing WordPress Errors
- Reinstalling WordPress core as a first response, when the actual fault is almost always a specific plugin, theme, or hosting-layer setting.
- Deactivating and reactivating plugins one at a time on the live site during business hours, when a staging copy would let you find the culprit without visitor-facing downtime.
- Ignoring the error log entirely and trying random fixes based on the visible symptom (a blank page) instead of the actual PHP error behind it.
- Editing wp-config.php without a backup copy first, turning a recoverable error into a site that won't load at all if a typo is introduced.
- Assuming a 500 error is always WordPress's fault, when server-level misconfiguration and generic PHP failures produce the identical message.
Wrapping Up
In short, the white screen, 500 errors, memory exhaustion, and broken permalinks that make up most WordPress troubleshooting requests all trace back to a small set of root causes — plugin/theme conflicts, PHP limits, .htaccess corruption, or database issues — each with a specific, repeatable fix. Enabling debug mode and reading the actual error, rather than guessing from the visible symptom, is the one habit that turns a stressful outage into a five-minute fix.