How to Fix the WordPress White Screen or "Critical Error"

Two of the most common WordPress problems look like this:

• a completely blank white page (the "white screen of death"), or
• "There has been a critical error on this website."

Both mean PHP hit a fatal error - almost always caused by a plugin, a theme, PHP memory running out, or a PHP version the code doesn't support. This guide shows how to find the cause and fix it in OpenPanel, even when you can't log in to wp-admin.

Step 1: Check the Recovery Email​

For a critical error, WordPress emails the site's admin address with the subject "Your Site is Experiencing a Technical Issue". It names the plugin or theme that failed and contains a recovery mode link that lets you log in with that plugin disabled.

If you got the email, follow the link, deactivate or update the named plugin, and you're done. If not, continue.

Step 2: Turn On Debugging and Read the Error​

1. Open OpenPanel → WordPress and click Manage on the site.
2. Go to the Debugging tab and enable WP_DEBUG and WP_DEBUG_LOG (leave WP_DEBUG_DISPLAY off on a live site, so visitors don't see errors).
3. Reload the broken page.
4. Open wp-content/debug.log in the File Manager and scroll to the bottom.

You'll see a line like:

PHP Fatal error:  Uncaught Error: Call to undefined function ... in /var/www/html/example.com/wp-content/plugins/some-plugin/some-file.php:123

The path tells you the culprit - here, the some-plugin plugin.

Also check the PHP container's log in Containers → Logs for the domain's PHP container (e.g. php-fpm-8.3).

Step 3: Fix the Cause​

A plugin​

Disable the plugin without wp-admin, in the File Manager: rename its folder, e.g. wp-content/plugins/some-plugin → some-plugin.off. WordPress deactivates it automatically.

Not sure which plugin? Rename the whole wp-content/plugins folder to plugins.off. If the site comes back, rename it back and disable plugins one by one to find the broken one.

With WP-CLI you can do the same in one line - see Use WP-CLI:

wp plugin deactivate some-plugin --allow-root
wp plugin deactivate --all --allow-root

The theme​

If the error points to wp-content/themes/your-theme/, rename that theme's folder. WordPress falls back to a default theme (install one, like Twenty Twenty-Five, if none is present).

PHP memory limit​

If the log says Allowed memory size of ... bytes exhausted, raise PHP's memory_limit to 256M or 512M - see How to increase PHP memory_limit. You can also add to wp-config.php:

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

PHP version​

After switching PHP versions, old plugins can break (Deprecated, Fatal error: Uncaught TypeError, Call to undefined function). Switch the domain back to the previous PHP version, then update the plugin - see Change the PHP version per domain.

A failed update​

If an update was interrupted, delete the .maintenance file from the site root, then reinstall WordPress core from WP Manager's Security tab (Reinstall WordPress core) - this replaces core files without touching your content.

Step 4: Restore a Backup (If Nothing Else Works)​

If the site broke after a change you can't undo, restore the last working backup from WP Manager's Backups tab (files, database or both) or from the account Backups.

Other Blank-Page Causes​

Related​

• WP Manager - Debugging
• Set up a WordPress staging site - test updates before they break production