If you are a WordPress user, chances are you have faced the frustrating error: “Updating failed. The response is not a valid JSON response.” This error usually appears when you try to publish or update a post/page in the WordPress block editor (Gutenberg). For beginners, it can feel confusing and intimidating, but the good news is—it is completely fixable.
In this article, we’ll dive deep into what causes this error, why it happens, and the most effective ways to fix it. Whether you are a blogger, business owner, or developer, by the end of this article, you’ll have a complete understanding of how to resolve this issue step by step.
Table of Contents
What Does “Updating failed. The response is not a valid JSON response” Mean?
This error is related to WordPress REST API communication issues. The REST API allows WordPress to send and receive data between the server and your browser. When something interrupts this communication, WordPress cannot update your post or page and shows the error.
In simple words:
- WordPress tries to save your post.
- Your browser communicates with the server using the REST API.
- If the server response is not in proper JSON format (JavaScript Object Notation), WordPress doesn’t understand it.
- As a result, it throws the “Updating failed. The response is not a valid JSON response” error.
Common Causes of the JSON Response Error in WordPress
Before fixing the problem, it’s important to know why it happens. Here are the most common causes:
- Incorrect WordPress URL settings – If your WordPress Address (URL) and Site Address (URL) don’t match correctly.
- SSL/HTTPS issues – Improper SSL setup can break communication.
- Permalink structure issues – Broken permalinks often cause API failures.
- Plugin conflicts – Some plugins may block or modify API requests.
- Theme conflicts – Poorly coded themes can interfere with the REST API.
- Security/firewall restrictions – Security plugins or server firewalls may block JSON requests.
- .htaccess misconfiguration – Incorrect rewrite rules can block requests.
- Mixed content (HTTP/HTTPS conflict) – If your site loads resources from both HTTP and HTTPS.
- Server-side issues – PHP version, memory limits, or hosting restrictions.
Now that you know the causes, let’s move to the solutions.
Step-by-Step Solutions to Fix the JSON Response Error in WordPress
Here’s a list of proven solutions you can try. You don’t need to apply all of them—just follow step by step until the error is fixed.
1. Check WordPress and Site Address Settings
Go to:
- Dashboard → Settings → General
- Ensure that WordPress Address (URL) and Site Address (URL) are the same.
- If your site uses SSL, both should start with
https://.
For example:
✅ Correct: https://example.com
❌ Incorrect: http://example.com vs https://example.com
After saving changes, try updating your post again.
2. Fix SSL/HTTPS Issues
If you recently added an SSL certificate, your site may still be loading some insecure content.
- Install the free plugin: Really Simple SSL.
- Activate it to automatically fix mixed content issues.
- Clear your browser cache and try updating again.
3. Reset Permalink Settings
Broken permalinks often cause the REST API to fail.
- Go to Dashboard → Settings → Permalinks.
- Select Plain and save changes.
- Then, switch back to your preferred permalink structure (e.g., Post Name) and save again.
This refreshes your .htaccess file and often fixes the issue.
4. Disable Plugins Temporarily
Plugin conflicts are a major cause of this error.
- Go to Dashboard → Plugins → Installed Plugins.
- Deactivate all plugins.
- Try updating a post/page again.
If the error disappears, reactivate plugins one by one to find the problematic plugin.
5. Switch to a Default Theme
Themes can also break JSON requests if they have custom scripts or outdated code.
- Go to Appearance → Themes.
- Switch to a default theme like Twenty Twenty-Five.
- Test again.
If the problem is solved, your old theme is the issue. You may need to update or replace it.
Read more – Best Free WordPress Blog Themes
6. Check .htaccess File
The .htaccess file controls how WordPress handles URLs. A broken file can cause JSON issues.
- Connect to your site via FTP or File Manager.
- Locate the
.htaccessfile in the root directory. - Backup the file before editing.
- Replace it with the default WordPress rules:
# 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
Save changes and check if the error is gone.
7. Increase PHP Memory Limit
Sometimes, low server memory causes incomplete API responses.
- Edit your wp-config.php file.
- Add the following line before
/* That's all, stop editing! */:
define('WP_MEMORY_LIMIT', '256M');
Save the file and test again.
8. Check REST API Status
You can verify if your REST API is working correctly:
- Go to Tools → Site Health → Status.
- Look for REST API under “Critical Issues.”
If there’s a warning, follow WordPress’s recommendation to fix it.
9. Fix Mixed Content Issues
If your site loads images, CSS, or JS files over http:// while the site runs on https://, it can break JSON responses.
- Use the Why No Padlock tool to check for mixed content.
- Update your links in Database or using the Better Search Replace plugin.
10. Contact Your Hosting Provider
If none of the above works, the issue might be server-related.
- Contact your hosting provider’s support team.
- Ask them to check firewall restrictions, PHP error logs, and mod_security rules.
A good host will fix server misconfigurations quickly.
Preventing the JSON Response Error in the Future
Once you fix the issue, follow these best practices to prevent it from happening again:
- Always keep WordPress, themes, and plugins updated.
- Use a reliable hosting provider with proper server configuration.
- Install an SSL certificate properly.
- Regularly check Site Health under Tools.
- Avoid poorly coded plugins and themes.
- Backup your site frequently.
FAQs About the JSON Response Error in WordPress
Here are some common questions users ask about this error:
1. Why does WordPress show “Updating failed. The response is not a valid JSON response”?
Because WordPress cannot communicate with the server properly via the REST API. The response it receives is not in valid JSON format.
2. Will this error break my website?
No, it only prevents you from updating posts/pages. However, if not fixed, it can disrupt your workflow.
3. Can a plugin cause this error?
Yes, plugins that modify API requests, security plugins, or caching plugins can trigger this error.
4. Does changing the permalink structure fix this issue?
Yes, resetting permalinks often resolves this error by refreshing .htaccess rules.
5. Is this error related to SSL certificates?
In many cases, yes. Improper SSL setup or mixed content issues can cause JSON errors.
6. How can I test if my REST API is working?
Go to Tools → Site Health → Status in WordPress to check if REST API is accessible.
7. Can hosting cause this error?
Yes, strict firewalls, mod_security, or server restrictions can block REST API requests.
8. What should I do if nothing works?
Contact your hosting provider and ask them to review server settings and error logs.
Conclusion
The “Updating failed. The response is not a valid JSON response” error in WordPress can feel overwhelming at first, but it is usually easy to fix once you understand the causes. Most of the time, it’s related to permalink issues, SSL configuration, or plugin conflicts. By carefully following the steps in this guide—checking URLs, resetting permalinks, disabling plugins, fixing .htaccess, and reviewing server settings—you can quickly resolve the issue and get back to publishing content without stress.
WordPress errors may seem complicated, but with the right troubleshooting approach, you can always find a solution. Keep your site updated, use reliable plugins, and maintain good hosting practices to prevent such issues in the future.
