WordPressの重大なエラー：原因と解決策

If you manage a ワードプレス website, you may eventually encounter one of the most frustrating messages in the ecosystem: “There has been a critical error on this website.”

This issue, commonly referred to as the WordPress critical error, can suddenly prevent your website from loading. Instead of your normal pages, visitors see a blank screen or a simple error notice. For online stores, business websites, or content platforms, this can lead to lost traffic, lost revenue, and a poor user experience.

The good news is that a WordPress critical error is usually fixable. In many cases, the issue is caused by plugin conflicts, theme problems, PHP memory limits, or server configuration errors.

In this guide, we’ll explain what the WordPress critical error is, why it happens, and how to fix it step-by-step. Even if you’re not a developer, understanding these troubleshooting methods will help you quickly restore your website.

What Is the WordPress Critical Error?

The WordPress critical error is a fatal PHP error that prevents WordPress from executing properly. Instead of loading the website normally, WordPress stops running and displays an error message.

Most commonly, users see something like this:

“There has been a critical error on this website. Please check your site admin email inbox for instructions.”

This message appears when WordPress detects a severe issue in the code that it cannot safely recover from.

Unlike minor warnings or notices, a WordPress critical error halts the entire site. In many cases, both the frontend and the admin dashboard become inaccessible.

For business websites or eCommerce stores, this type of error can be particularly serious because the site may be offline until the problem is resolved.

Why Does the WordPress Critical Error Happen?

Understanding the causes of the WordPress critical error helps you fix it faster. While there can be many technical triggers, most cases fall into a few common categories.

Plugin Conflicts

Plugins extend WordPress functionality, but they can also introduce problems.

A WordPress critical error often happens when:

• A plugin update introduces incompatible code
• 2つのプラグインが競合しています
• A plugin uses outdated PHP functions
• A plugin is partially installed or corrupted

Because plugins interact deeply with WordPress core, even a small coding error can cause a fatal crash.

Theme Issues

Themes control the visual appearance of your site, but they also contain code.

If a theme includes incompatible PHP code or conflicts with WordPress updates, it may trigger a WordPress critical error.

Common theme-related causes include:

• Poorly coded custom themes
• Outdated theme files
• Compatibility problems after WordPress updates
• Missing or corrupted template files

PHP Version Problems

WordPress relies heavily on PHP. If your hosting environment runs an incompatible PHP version, certain functions may fail.

例えば：

• A plugin may require PHP 8.0 while your server runs PHP 7.2
• A theme may rely on functions removed in newer PHP versions

When this happens, WordPress may display a critical error because it cannot execute the code properly.

Memory Limit Exhaustion

Every website has a memory allocation defined by the server. When WordPress exceeds this limit, scripts fail to execute.

Heavy plugins, large queries, or inefficient code can cause the site to exceed available memory, resulting in a WordPress critical error.

Corrupted Core Files

Sometimes the issue lies in the WordPress core itself.

This may occur when:

• A WordPress update fails
• Files are accidentally modified
• Malware alters the core installation

When essential files are missing or damaged, WordPress cannot run properly.

First Step: Check Your Admin Email

When a WordPress critical error occurs, WordPress often sends a diagnostic email to the site administrator.

This message may include:

• The plugin responsible for the error
• The theme involved
• The exact PHP file causing the crash
• A temporary recovery link

The recovery link allows you to log into the admin dashboard in Recovery Mode, even if the site is broken.

Before trying more advanced fixes, always check the administrator email associated with your WordPress installation.

Method 1: Disable All Plugins

If a plugin conflict caused the WordPress critical error, disabling plugins is usually the fastest fix.

How to Disable Plugins via FTP

1. Connect to your website using FTP or your hosting file manager.
2. Navigate to the folder:

/wp-content/

3. Locate the folder named:

プラグイン

4. Rename the folder to something like:

plugins-disabled

By renaming the folder, WordPress automatically deactivates all plugins.

If your website loads normally afterward, you know a plugin caused the WordPress critical error.

You can then restore the folder name and reactivate plugins one by one to find the culprit.

Method 2: Switch to a Default Theme

If disabling plugins does not fix the issue, the next step is checking the theme.

A problematic theme may cause a WordPress critical error, especially after updates.

To test this:

1. Access your site via FTP or file manager
2. Navigate to:

/wp-content/テーマ/

3. アクティブなテーマフォルダの名前を変更する

WordPress will automatically switch to a default theme like Twenty Twenty-Four if available.

If the site starts working again, the theme likely caused the critical error.

Method 3: Increase PHP Memory Limit

Sometimes WordPress simply runs out of memory.

Increasing the memory limit can resolve the WordPress critical error.

Edit the wp-config.php file and add:

'WP_MEMORY_LIMIT'、'256M'を定義します。;

This increases available memory for WordPress processes.

After saving the file, refresh your website to see if the error disappears.

Method 4: Enable WordPress Debug Mode

Debug mode helps identify the exact cause of the WordPress critical error.

To enable debugging, open wp-config.php and add or modify:

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

This allows WordPress to display detailed error information.

The output may reveal:

• The plugin responsible
• The file causing the crash
• The line number of the error

This information makes troubleshooting much easier.

Method 5: Reinstall WordPress Core Files

If the problem comes from corrupted core files, reinstalling WordPress can solve it.

You can do this without affecting your content.

手順:

1. Download a fresh WordPress package
2. Extract the files
3. Upload everything except:

wp-コンテンツ
wp-config.php

This replaces the core system files while keeping your content and settings intact.

Method 6: Check PHP Version Compatibility

Your hosting environment must support modern PHP versions.

Most WordPress installations work best with:

• PHP 8.0
• PHP 8.1
• PHP 8.2

If your hosting provider uses outdated PHP versions, plugins and themes may fail.

You can usually change the PHP version inside your hosting control panel.

Method 7: Restore from Backup

If troubleshooting becomes complicated, restoring a backup can quickly resolve a WordPress critical error.

Many hosting providers offer automatic backups. You can restore a version of the site before the error occurred.

Backup solutions like:

• server snapshots
• backup plugins
• hosting restore points

can help recover your site in minutes.

Preventing WordPress Critical Errors

While the WordPress critical error can usually be fixed, prevention is always better than repair.

Here are a few best practices:

Keep Plugins Updated

Outdated plugins are one of the most common causes of fatal errors.

Regular updates ensure compatibility with the latest WordPress versions.

Use Reliable Themes

Choose well-maintained themes with active support and frequent updates.

Poorly coded themes significantly increase the risk of crashes.

Maintain Regular Backups

Backups act as your safety net. If something goes wrong, you can quickly restore your site.

Use Quality Hosting

Cheap or unstable hosting environments often lead to server conflicts and memory issues.

A reliable hosting provider ensures proper PHP versions, stable memory limits, and consistent performance.

Test Updates in a Staging Environment

Before applying major updates, test them on a staging site.

This allows you to detect plugin or theme conflicts before they affect your live website.

Why Website Stability Matters for Online Businesses

For content sites, a WordPress critical error is frustrating.

For eCommerce stores or international businesses, it can be far more serious.

Website downtime affects:

• customer trust
• search engine rankings
• conversion rates
• brand credibility

Even a few hours of downtime during peak traffic can lead to significant losses.

That’s why many businesses invest in professional website design, performance optimization, and maintenance services to ensure stability.

最後に

その ワードプレス critical error may look intimidating at first, but in most cases it has a clear cause and a practical solution.

By understanding the most common triggers—such as plugin conflicts, theme issues, PHP limitations, or corrupted files—you can systematically troubleshoot and restore your website.

Whether you run a blog, a portfolio site, or an online store, maintaining a stable WordPress environment is essential for long-term success.

For businesses operating internationally, website reliability becomes even more important. A well-designed and professionally structured website not only reduces the risk of technical issues but also improves user experience and conversion performance.

This is exactly where our expertise comes in. At エアサン, we specialize in cross-border eCommerce website design, helping brands build high-performance websites that are visually compelling, user-friendly, and optimized for global audiences.

If your business needs professional support with WordPress or Shopify website design, our team can help you create a site that is both stable and conversion-focused. Feel free to reach out and explore how we can bring your digital vision to life.