How to Fix the WordPress “Publishing Failed. The Response Is Not A Valid JSON Response” Issue

One of the most frustrating errors you can encounter while managing your WordPress website is the dreaded “Publishing Failed. The Response Is Not A Valid JSON Response” message. This sudden roadblock usually appears in the Gutenberg block editor right when you try to publish or update a page or post, halting your content workflow entirely.

At SiteSuraksha, we help businesses maintain secure, high-performing WordPress websites. In this guide, we will break down why this error occurs and walk you through the most effective ways to resolve it quickly.

Why Does the “Not a Valid JSON Response” Error Happen?

To understand the error, it helps to know how WordPress communicates behind the scenes. When you save or publish content, the editor sends a request to your server, and WordPress expects a specific JSON response to confirm the action was successful.

If that communication breaks down—due to a misconfigured URL, a plugin conflict, a corrupted `.htaccess` file, or server issues—WordPress cannot read the response, triggering this error. Common culprits include:

• Incorrect WordPress Address (URL) settings
• Broken or misconfigured permalink structures
• Issues with the REST API
• Plugin or theme conflicts
• Incorrect file permissions or server firewall rules

How to Fix the JSON Response Error in WordPress

1. Check Your WordPress and Site URL Settings

An inconsistency between your actual domain and what WordPress thinks your domain is can break REST API communications.

• Go to your WordPress Dashboard and navigate to Settings > General.
• Check the WordPress Address (URL) and Site Address (URL) fields.
• Ensure both URLs match and use the correct protocol (https:// if you have an SSL certificate installed).
• Save your changes and test the editor.

2. Reset Your Permalinks

Corrupted permalink structures are a frequent cause of JSON errors because they disrupt how URLs are parsed.

• Go to Settings > Permalinks in your dashboard.
• Scroll to the bottom and click Save Changes (you don’t need to change anything; simply re-saving flushes the rewrite rules).
• Check if the publishing error persists.

3. Check the Health of Your WordPress REST API

The Gutenberg editor relies heavily on the WordPress REST API to save content. If something is blocking the API, you will see JSON errors.

• Go to Tools > Site Health in your dashboard.
• Look for any critical issues related to the REST API or loopback requests.
• If you notice errors here, it often points to a firewall, security plugin, or server-level restriction blocking API requests. Whitelist the REST API or temporarily disable security rules to test.

4. Test for Plugin and Theme Conflicts

Third-party plugins—especially security, caching, or SEO plugins—can sometimes interfere with the block editor.

• Deactivate all your plugins temporarily.
• Try publishing a test post. If the error disappears, reactivate your plugins one by one until you find the culprit.
• If the issue remains, temporarily switch to a default WordPress theme (like Twenty Twenty-Four) to rule out theme-level issues.

5. Regenerate Your .htaccess File

If you are using an Apache server, a corrupted `.htaccess` file can break URL routing and JSON responses.

• Connect to your website via FTP or your hosting file manager.
• Locate the `.htaccess` file in your root directory and download a backup copy.
• Delete the file from the server.
• Go to Settings > Permalinks in WordPress and click Save Changes to generate a fresh `.htaccess` file.

Need Expert Help?

Troubleshooting server errors and plugin conflicts can be time-consuming and distracting from running your business. If you’d rather leave it to the professionals, SiteSuraksha provides comprehensive WordPress security and maintenance services to keep your site running smoothly, securely, and error-free around the clock.