Customizer Not Loading – Blank Screen or Page Not Found

If the Customizer under Appearance is not loading or showing a blank screen, or displaying a “Page Not Found” error, this guide covers the most common causes and how to fix them.

The blank screen in the customizer area is a common scenario if you have resource exhaustion.

Reasons

There could be multiple reasons why this could be happening. In this document, we will provide you with the guidelines of why this could happen and how to resolve this. The most common reasons are:

• Low PHP memory limit
• Low resources allocation on your account by your hosting provider
• Poor performance on your hosting account
• Resource limit exhaustion
• Server-level security software (ModSecurity) blocking the Customizer request

Let’s talk about how to fix these issues.

Step 1: Back to basics

The first and foremost step to resolve this issue is to deactivate all plugins temporarily and see if that solves the problem. Then, activate plugins to see which plugin is causing the problem. If this is related to a plugin which is causing conflict, you can either deactivate the plugin permanently or contact the plugin creator for a solution.

It is also a good idea to check if the issue is related to the theme. Please try switching to another theme, like Twenty Twenty -One, and check whether the issue persists. If yes, then it is not the theme causing the error.

Step 2: PHP memory limit

Once you have confirmed that the issue is not related to a plugin or the theme, you will need to check the PHP memory limit of your website. Please navigate to the Tools>Site Health.

Click on the Info tab

Scroll down to the server option and ensure that the PHP memory limit is set to a minimum of 256M and the upload max file size is set to 60M.

In case if the above settings are not updated on your website, you can either change it by logging into the control panel of your hosting account or contact the hosting provider and they will change it for you.

Step 3: Low resources

Most of the time, the hosting providers set lower resources that you are eligible for in your account which might result in the customizer being blank. Please contact the hosting provider and ask for the maximum resources to be allocated to your account. This will ensure that you never run out of resources when the website is trying to load on the server.

Step 4: Resource Limit Exhaustion (This Almost Always Fixes It)

If your Customizer is not loading, showing a blank screen, keeps loading without displaying any options, or shows a “Page Not Found” error, this step is most likely the fix. In most cases, these issues are caused by your website exceeding the Apache server’s response body limit, which prevents the Customizer from loading completely.

It is recommended to take a backup of your website before editing the .htaccess file manually. Here is an article that will explain how to take a backup of your website.

Editing .htaccess File From cPanel

Log into your hosting account, navigate to cPanel and select File Manager.

From the File Manager, go to the public_html folder. The .htaccess file is located in this folder. When you find it, right-click and select Edit.

Add the following code onto your htaccess file and click on save and close.

<IfModule mod_substitute.c>
SubstituteMaxLineLength 20m
</IfModule>

This should resolve the issue and you will get the customizer options on your website.

This should resolve the issue and the Customizer options will load correctly on your website.

Step 5: ModSecurity (ModSec) Blocking the Customizer

If the .htaccess fix in Step 4 does not resolve the issue and you are still seeing a “Page Not Found” error when opening the Customizer, the server may be running ModSecurity (ModSec), a web application firewall that some hosting providers enable by default.

When ModSec has a low response body memory limit configured, it can block the Customizer request entirely and return a “Page Not Found” error instead of the Customizer interface.

In this case, contact your hosting provider and ask them to:

1. Check whether ModSecurity is blocking requests to the WordPress Customizer.
2. Increase the response body memory limit in their ModSec configuration.

Once the limit is raised, the Customizer should load correctly without any further changes needed on the WordPress side.