Updating Failed. The Response is Not a Valid JSON Response

Updated On:

June 20, 2025

,By

Kishore Sahoo

How to Fix “Updating Failed. The Response is Not a Valid JSON Response” in WordPress

If you’ve encountered the frustrating “Updating Failed. The Response is Not a Valid JSON Response” error while editing a post or page in WordPress, you’re not alone. This is a common issue, especially with the Gutenberg block editor, and typically means that WordPress was expecting a JSON-formatted response from the server—but got something else instead.

In this guide, we’ll explain what causes the error and walk you through step-by-step fixes.

What Causes This Error?

WordPress uses the REST API behind the scenes to communicate between the editor and the server. If something breaks that communication—like a misconfigured server, plugin conflict, or security block—WordPress may receive an HTML error, an empty string, or invalid content instead of JSON.

This triggers the error message:
“Updating failed. The response is not a valid JSON response.”

✅ How to Fix It (Step-by-Step)

1. Reset Permalinks

Sometimes a quick reset of permalinks solves the issue.

Go to Settings > Permalinks.
Click “Save Changes” without changing anything.

This refreshes your rewrite rules and often resolves REST API issues.

2. Check Your Site Address (URL)

Make sure the URLs in Settings > General are correct:

WordPress Address (URL)
Site Address (URL)

They should:

Use https:// if you have SSL.
Match your actual domain (avoid www mismatches like https://example.com vs https://www.example.com).

3. Fix .htaccess File (Apache Servers Only)

If you’re on an Apache server, your .htaccess file might be broken.

Use this standard WordPress .htaccess:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

You can edit this via FTP or File Manager in cPanel.

4. Test the REST API

Visit this URL in your browser:

https://yourdomain.com/wp-json/

✅ If you see a JSON response — good!
❌ If you see a white screen, 403/500 error, or HTML — something is wrong.

In that case, continue with the following steps.

5. Disable Plugins Temporarily

One of your plugins may be interfering with the REST API.

Deactivate all plugins.
Try editing a post or page again.
If it works, reactivate plugins one by one to find the culprit.

Plugins that add security, caching, or custom headers are the most likely offenders.

6. Switch to a Default Theme

Themes can also cause this issue if they enqueue scripts incorrectly or interfere with REST.

Go to Appearance > Themes.
Activate a default theme like Twenty Twenty-Four.
Test the editor again.

If the problem goes away, the issue lies within your original theme.

7. Fix SSL or Mixed Content Issues

If your site loads over HTTPS but references insecure resources (HTTP), it can break REST API responses.

Install the plugin Really Simple SSL.
Check that your site fully loads over HTTPS (no red warnings or blocked content).

8. Check Browser Console and Network Tab

Use Developer Tools in your browser:

Open Console → Look for JavaScript errors.
Open Network tab → Look for failed wp-json requests or 403/500 errors.

This can help pinpoint which request is breaking and what response is returned.

9. Check ModSecurity or Hosting Firewall

Many shared hosts use firewalls like ModSecurity, which sometimes block REST API requests thinking they’re malicious.

Contact your hosting provider.
Ask them to check if /wp-json/ is being blocked.
Whitelisting or disabling specific ModSecurity rules may solve the issue.

10. Enable WordPress Debug Mode

Turn on debugging to catch PHP errors that may be interfering with REST:

In your wp-config.php file, add:

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

Then check wp-content/debug.log after triggering the error.

11. Increase PHP Memory Limit

If your server is low on memory, the editor might fail to return a full response.

Add this to your wp-config.php:

define( 'WP_MEMORY_LIMIT', '256M' );

12. Install Health Check Plugin

Use Health Check & Troubleshooting to:

Detect REST API issues
Run in “troubleshooting mode” without affecting site visitors
Check for critical errors

13. Remove the featured image

Try to remove the images:

Remove all images
Add different images if possible
Check for image formats.

Summary of Fixes

Fix	Description
Reset Permalinks	Flushes URL rules
Correct Site URL	Avoids mixed domain/SSL issues
.htaccess Fix	Enables proper routing
Plugin/Theme Conflict	Temporarily disable them to test
REST API Access	Check response from `/wp-json/`
Enable Debugging	Logs hidden PHP issues
Contact Host	Whitelist ModSecurity or firewall blocks

Final Thoughts

While the “Updating Failed. The Response is Not a Valid JSON Response” error can seem vague, it almost always comes down to a miscommunication between the editor and server—often caused by plugins, permalinks, or server configuration.

Take it one step at a time, and you’ll usually find the issue in minutes. If you’re still stuck, leave a comment or contact your host for help.