WordPress Critical Error – When you’re locked out and the frontend is entirely down, you need to know how to fix the critical error now. Every minute that passes is driving away visitors as they encounter a glaring error screen.

How to Fix the WordPress Critical Error

You’re here to get your site up and running again, and to that end, I’ve collected several different potential ways to fix the issue. Knowing that the cause is likely PHP-related, these may involve editing core WordPress files. Even with your site in a broken state, make sure to back it up before implementing any of these suggestions, as I don’t want to make it worse!

Enable Debug in WordPress

If you’re having trouble with WordPress, one of the first things you should do is enable debugging. With debug mode on, you’ll be able to see the various PHP errors occurring on your site, and you can use this to trace back to the root of the issue.

As you may be unable to access your dashboard, you’ll also need to enable the debug log. This will write all PHP errors to a file.

If you need to manually turn on debugging, or you need to access the debug log, follow these steps.

Step 1: Connect to your site with FTP.

Step 2: Find wp-config.php in the root folder and open it with a text editor or IDE.

Step 3: Place the following code at the bottom of the document, just before the final message, then save and close the file:

define( ‘WP_DEBUG’, true );

define( ‘WP_DEBUG_DISPLAY’, false );

define( ‘WP_DEBUG_LOG’, true );

Debugging is now enabled on your site and errors will be written to the log. You can find the debug log in the wp-content folder, named debug.log.

Look for names of your theme or plugins which will point to them being the cause or references to a specific file. Even if you aren’t sure what to do with this information, save it someplace — it can help you if you need to reach out for support.

When you’re finished debugging, make sure to remove these lines of code.

Roll Back Your Site

When WordPress errors rear their head, restoring a backup can be a quick and easy way out. While it won’t always solve the issue, it’s definitely worth a shot. And if the problem happens again, you may be able to retrace your steps next time.

How you restore your website all depends on how you backed it up. If you use a plugin, follow the instructions in the documentation. If backups are included with your web host, you’ll likely be able to do it from your hosting dashboard.

Before restoring to your live site, try it on a staging site to ensure that the site is indeed functioning and you’re not overwriting your hard work.

Revert to a Default Theme

Sometimes the critical error can be traced back to a conflict within your theme. The best way to test for this is to temporarily delete it and revert to a default theme, which should immediately clear up the issue.

Make sure you back up your site first, as you’ll need a way to get your theme files back once they’re gone. Simply reinstalling the theme may cause you to lose your custom styling.

If you have access to your dashboard, this is easy. Just go to Appearance > Themes, click on the theme to select it, and then click Delete in the lower right corner of the pop-up window.

If you don’t see the option, then try downloading and switching to a different theme. The safest bet is to try a default theme like Twenty Twenty-One.

If you don’t have access to your backend, follow these instructions to revert to a default theme with FTP.

Step 1: Connect to your site with FTP.

Step 2: Navigate to wp-content/themes. You have two choices here: either rename your theme folder (will allow you to turn the theme back on later) or simply delete it.

Step 3: If you don’t have a backup theme here already, manually download Twenty Twenty and place its files into the themes folder.

Your site should now revert to Twenty Twenty. If it loads properly now, you know it was a theme conflict.

To restore your theme files, simply reinstall the theme or change the folder back to its original name.

Disable All Plugins

When you’re having a critical error, a plugin is often to blame. If you have several or even dozens of plugins on your site, trying to locate the one that’s the issue may seem like a daunting task.

But there’s an easy way to find the problem plugin: simply turn them all off and see if that fixes the problem. If it does, enable them one by one until your site breaks again. And there’s the culprit!

To disable your plugins from the dashboard, visit Plugins > Installed Plugins and tick the checkbox at the top of the list to select them all. Then click Bulk Actions > Deactivate, which should be enough to disable any conflicts and restore your site.

You can also click Delete instead to entirely remove their files, though you will need to reinstall them manually or restore a backup.

Then turn them on one by one by returning to Installed Plugins and clicking Activate on each.

You can do essentially the same thing through FTP.

Step 1: Log in to your site with FTP.

Step 2: Open the wp-content folder to find your plugins.

Step 3: Rename the plugins folder to plugins_old and verify that your site is working again.

Step 4: Rename the folder back to “plugins”. The plugins should be disabled still, so you should be able to log in to your dashboard and activate them one by one. If the plugins reactivate automatically, rename individual plugin folders with _old until your site is restored. Let’s move on to the next tip to Fix the WordPress Critical Error.

Raise the PHP Memory Limit

Even if a plugin or theme is the cause of your broken website, the PHP memory limit is often the real one to blame.

What is the PHP memory limit? Your web server only has a certain amount of RAM, or memory, so WordPress sets a hard limit on how much memory a single PHP script can take up. When this limit is exceeded, you’ll encounter the white screen of death or the critical error.

While you don’t want to set the memory limit too high and allow misconfigured scripts to slow your site to a crawl, the default value may be far too low. Raising your PHP limit just a bit could instantly fix your broken website.

Step 1: Access your site through FTP and open wp-config.php.

Step 2: Insert the following code right before the final line and save.

define( ‘WP_MEMORY_LIMIT’, ‘128M’ );

You can also try 256M if this doesn’t fix the issue, but anything higher is definitely unnecessary unless specifically called for in plugin documentation. If the issue is with the memory limit, the plugin you’re using is almost certainly broken and needs to be disabled. Let’s move on to the next tip to Fix the WordPress Critical Error.

Raise the Max Upload File Size and Text Processing Functions

If you’re only seeing the critical error in certain situations and not constantly on every page, a small tweak to a few PHP functions might be able to fix it.

Uploading large files and finding yourself on an error screen is probably a result of the max upload file size being too small, while certain large pages breaking can be fixed by increasing recursion and backtrack limits.

First, check what your maximum upload size is and compare it to the file you’re trying to upload. You can find this by visiting Media > Add New and checking beneath the file uploader.

To fix either of these issues, you’ll need to log into FTP and edit the wp-config.php file, placing the new code right above the final comment line.

To increase the max upload file size, add this code:

ini_set(‘upload_max_size’ , ‘256M’ );

ini_set(‘post_max_size’,’256M’);

And to fix the breaking of large pages on your site, add this code:

ini_set(‘pcre.recursion_limit’,20000000);

ini_set(‘pcre.backtrack_limit’,10000000);

Let’s move on to the next tip to Fix the WordPress Critical Error.

Clear Your Site Cache

Caching is a great way to speed up your website, and most of the time it’s strictly a good thing. But sometimes the cache can get corrupted, leaving your site throwing out errors.

When this happens, a simple solution is to clear the cache, which should be all you need to get rid of the problem and restore your site to working order.

No fear: The cached version of your pages will soon be restored, allowing your site to load quickly again. Clearing the cache will simply delete the stuck corrupted files.

Upgrade Your PHP Version

Outdated PHP can cause your site to break, and other conflicts are sure to occur. You usually want your site on the latest version of PHP supported by WordPress, which is currently PHP 7.3 to 8.0.

Some WordPress users prefer to stay on PHP 7.4 as they’re concerned about theme and plugin compatibility. Usually, this won’t cause problems. But if you’re using PHP 5.x, it’s imperative you upgrade as it can cause serious conflicts.

A PHP upgrade is a big deal, so make sure you have a backup ready before trying it.

That is all from How to Fix the WordPress Critical Error in Website.