{"id":4009,"date":"2026-07-30T07:34:55","date_gmt":"2026-07-30T07:34:55","guid":{"rendered":"https:\/\/www.wpchatsupport.com\/blog\/?p=4009"},"modified":"2026-07-30T07:56:46","modified_gmt":"2026-07-30T07:56:46","slug":"how-to-fix-the-not-a-valid-json-response-error-in-wordpress","status":"publish","type":"post","link":"https:\/\/www.wpchatsupport.com\/blog\/how-to-fix-the-not-a-valid-json-response-error-in-wordpress\/","title":{"rendered":"How to Fix the “Not a Valid JSON Response” Error in WordPress (Complete Guide)"},"content":{"rendered":"

Introduction<\/strong><\/h2>\n

The \u201cnot a valid JSON response\u201d error is common in WordPress. It usually appears when you update or publish a post or page. You may see this message: \u201cUpdating failed. The response is not a valid JSON response.\u201d You may also see: \u201cPublishing failed. The response is not a valid JSON response.\u201d<\/p>\n

This issue is also known as a WordPress JSON response error. Some users call it a Gutenberg JSON error because it appears in the WordPress block editor. It can stop you from saving your latest changes.<\/p>\n

In most cases, your content is not the problem. The issue happens when WordPress cannot get the right reply from your server. WordPress sends a request when you click Update or Publish. The server should send back a valid JSON response. If the response is broken, blocked, or redirected, WordPress shows this error.<\/p>\n

The good thing is that this error can usually be fixed. You only need to check the main causes one by one. In this guide, we will explain what the error means, why it happens, and how to fix it safely.<\/p>\n

What Does \u201cNot a Valid JSON Response\u201d Mean in WordPress?<\/h2>\n

The error sounds technical, but it is simple to understand. WordPress uses JSON to send and receive data. JSON is a format that helps WordPress and your server communicate.<\/p>\n

When you click Update or Publish, WordPress sends your content to the server. The server should return a clean JSON response. If WordPress receives the correct response, your content saves properly.<\/p>\n

The problem starts when the server sends something else. It may send a 404 page, 403 page, login page, redirect page, firewall block, PHP warning, or server error. WordPress cannot read these as valid JSON. So, it shows the WordPress update failed error.<\/p>\n

This is why the error is often linked with the REST API. The WordPress block editor uses the REST API to save content. If the REST API is blocked or not working, the editor may fail. To fix WordPress REST API issues, you need to check permalinks, plugins, security settings, and hosting rules.<\/p>\n

Sometimes, the content may still save even after the error appears. This happens when WordPress saves the content but receives a broken final response. Other times, the content may not save at all.<\/p>\n

In simple words, the WordPress block editor error means WordPress expected a proper server reply but received the wrong response. Once the communication issue is fixed, the editor usually works again.<\/p>\n

Common Causes of the WordPress JSON Response Error<\/strong><\/h3>\n

The WordPress JSON response error can happen for different reasons. Below are the most common reasons for the invalid JSON response WordPress issue.<\/p>\n

Broken permalink settings can stop WordPress from reading the right page<\/h4>\n

Permalink settings are one of the most common causes. WordPress uses permalinks to create clean URLs for posts, pages, and other content. It also uses rewrite rules to handle internal requests. If these rules stop working, WordPress may not find the correct REST API route. Instead of a JSON response, the server may return a 404 page. This can lead to a WordPress update failed message in the editor.<\/p>\n

Incorrect WordPress Address or Site Address can create redirects<\/h4>\n

Wrong site URL settings can also cause this issue. WordPress has two important URL fields. These are WordPress Address and Site Address. Both should use the correct domain. Both should also use the same HTTP or HTTPS version.<\/p>\n

This issue is common after adding SSL. It can also happen after moving a website to a new domain. Checking both URLs is a simple but important step.<\/p>\n

REST API is blocked or not working correctly<\/h4>\n

The WordPress REST API helps the editor communicate with your site. The block editor uses it when you save, update, or publish content. If the REST API is blocked, WordPress may not save changes properly. This can create a WordPress REST API error in the editor or Site Health.<\/p>\n

Plugin or theme conflicts can break the editor response<\/h4>\n

Plugins can also cause the invalid JSON response WordPress error. Security plugins may block REST API requests. Cache plugins may serve an old or broken response. Optimization plugins may change scripts or server output. Page builders and SEO plugins can also create conflicts in some cases.<\/p>\n

SSL or mixed content issues can affect saving content<\/strong><\/h4>\n

SSL issues can also create the WordPress block editor error. This usually happens when the website uses HTTPS, but some settings still use HTTP. Old internal links may also point to the HTTP version of the site. This can create mixed content or redirect problems.<\/p>\n

Firewall, ModSecurity, or Cloudflare rules may block requests<\/h4>\n

Security tools are useful, but they can sometimes block valid requests. A firewall may see a REST API request as suspicious. ModSecurity may block some POST requests from the editor. Cloudflare rules may also challenge or block admin requests.<\/p>\n

PHP warnings or server errors can damage the JSON response<\/h4>\n

PHP errors are another common cause. A plugin, theme, or custom code file may create a warning or fatal error. Even a small warning can break a clean JSON response. WordPress then receives extra output before the real response.<\/p>\n

How to Resolve the “Not a Valid JSON Response” Error in WordPress<\/strong><\/h3>\n

The WordPress JSON response error can often be fixed with simple checks. Start with the basic steps first. Then move to plugins, firewall, and server settings if needed. These steps can help fix the invalid JSON response WordPress issue safely.<\/p>\n

Step 1: Copy your content and take a backup first<\/h4>\n