How to Fix the Invalid JSON Error in WordPress (Beginner’s Guide)

By Naveed Ahmed | Reviewed by Syed Balkhi | April 26, 2024 | Reader Disclosure

Are you trying to fix the invalid JSON error in WordPress? This error appears when editing WordPress posts or pages on your website. You will see a message saying, ‘The response is not a valid JSON response’, and updating that page will fail.

In this article, we will show you how to easily fix the invalid JSON error in WordPress. We will also talk about why this error occurs and how to avoid it in the future. As a WordPress expert with over 15 years of experience, I’ve seen this error countless times, and I’m here to guide you through a step-by-step process to fix it.

What Causes the ‘Not a Valid JSON Response’ Error in WordPress?

The ‘Not a valid JSON response’ error in WordPress happens when WordPress fails to receive the expected response from the server. It’s like trying to have a conversation with someone who’s speaking a language you don’t understand. WordPress needs to communicate with the server in the background to function correctly. This communication uses a format called JSON (JavaScript Object Notation), which is a lightweight way to transport data.

If, for some reason, WordPress can’t get the response or the response isn’t in the right JSON format, you’ll see this error. It’s like the server is sending you gibberish, and WordPress doesn’t know what to do with it. The most common culprits are incorrect URL settings in WordPress or broken permalinks. Think of it like giving someone the wrong address to find you. They can’t reach you, and you can’t communicate.

How to Fix the Invalid JSON Error in WordPress

Here’s a comprehensive guide to fix the invalid JSON error in WordPress. Remember to always create a complete backup of your WordPress site before making any changes. This will allow you to restore your website to its previous state if something goes wrong.

Option 1. Check WordPress URLs in Settings

First, make sure your WordPress Address and Site Address settings are correct. Go to Settings » General page. Check the ‘WordPress Address (URL)’ and ‘Site Address (URL)’ fields. For most websites, these should be the same URL. However, if your Site Address is incorrect, it could trigger the invalid JSON error. If you made any changes, click ‘Save Changes’ and try editing a post or page to see if the error persists.

Option 2. Fix WordPress Permalink Structure

WordPress uses permalinks (SEO-friendly URLs) for your posts and pages. Sometimes, your permalink settings may be incorrect, causing the block editor to have trouble getting a valid JSON response. Go to Settings » Permalinks. Review the permalink options, and if unsure, choose one of the default formats. Save Changes and see if the error is gone.

Option 3. Regenerate WordPress .htaccess File

The .htaccess file manages SEO-friendly URLs. WordPress usually updates it automatically, but sometimes it needs a refresh. Click ‘Save Changes’ on the Permalinks settings page, and this might regenerate the file. If not, you need to access your website using an FTP client or your hosting account’s file manager. Locate the .htaccess file in your website’s root folder. Download it for backup and edit it. Replace the entire contents with the following code:

# BEGIN WordPress

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress

Save your changes and upload the .htaccess file back to your website. Try editing a post or page to see if the error is gone.

Option 4. View the REST API Debug Log

The invalid JSON error can also mean a problem with WordPress’s REST API. The REST API is the set of techniques WordPress uses to communicate with the server while you work on your website. Go to Tools » Site Health. Look for an issue labeled ‘The REST API encountered an unexpected result’. Clicking on it will show more details and may point to a plugin or third-party service causing the issue.

Option 5. Deactivate All WordPress Plugins

Plugin conflicts are another common cause. Go to Plugins » Installed Plugins. Select all plugins and choose ‘Deactivate’ from the ‘Bulk Actions’ drop-down menu. Click ‘Apply’ to deactivate all plugins. If the error disappears, one of your plugins is the culprit. Activate them one by one to identify the problematic plugin. You can then contact the plugin author for help or find an alternative.

Option 6. Temporarily Switch to the Classic Editor

The Classic Editor uses a simpler text editor and doesn’t rely heavily on the REST API, potentially avoiding the error. Install and activate the Classic Editor plugin. This will temporarily disable Gutenberg. Alternatively, you can use WPCode to disable Gutenberg safely. See our guide on how to disable Gutenberg with WPCode for more information.

Option 7. Switch to a Default WordPress Theme

Sometimes, a theme conflict can cause the error. Go to Appearance » Themes and activate a default theme like Twenty Twenty-Four or Twenty Twenty-Three. This will remove any custom code from your current theme. If the error disappears, it’s likely your theme was causing the issue.

Option 8. Temporarily Turn Off Website Application Firewall

Firewalls can sometimes block legitimate requests, leading to the error. If you’re using a WordPress firewall like Sucuri, Cloudflare, or a plugin, temporarily disable it. For plugins, simply deactivate them. For DNS-level firewalls, disable them from your account dashboard.

Option 9. Turn On Debugging in WordPress

WordPress has a built-in debugging feature. Add the following code to your wp-config.php file:

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

This will create a debug.log file in the /wp-content/ folder. Use an FTP client to access the file and see if it provides clues about the error.

Option 10. Check for Mixed Content Error

If your website is served over HTTPS (secure) but tries to load resources from an insecure HTTP source, it can trigger the error. Modern browsers block mixed content for security reasons. This is to prevent attackers from injecting malicious content into the secure website. Make sure all resources on your website are loaded from a secure HTTPS source.

Final Step: Seek Expert Help

If all else fails, the error could be caused by a misconfiguration on your WordPress hosting server. Contact your hosting provider for assistance. They are usually equipped to handle common WordPress issues.

Conclusion

The invalid JSON error can be frustrating, but with these steps, you can usually pinpoint the cause and resolve it. Remember to be patient, and use the process of elimination to identify the culprit. If you encounter any difficulties or are unsure about any of these steps, consult with a WordPress expert or your hosting provider for guidance.

FAQs

Frequently Asked Questions About Invalid JSON Error in WordPress

What is JSON?

JSON stands for JavaScript Object Notation. It’s a lightweight data-interchange format used for transmitting data between a server and a client. WordPress uses JSON for communication between its core functions and the server.

Why does WordPress use JSON?

JSON is efficient and easy for both humans and machines to read and write. It’s a simple and standardized way to transmit data quickly and efficiently. It’s also a popular format used by many web applications, making it a good choice for WordPress.

How do I find the .htaccess file on my website?

The .htaccess file is usually located in the root folder of your website. If you’re using an FTP client, navigate to the public_html or www folder. If you’re using your hosting account’s file manager, you’ll likely find it in the same location. You might need to enable the display of hidden files in your FTP client or file manager to see the .htaccess file.

What if the REST API debug log doesn’t provide any useful information?

If the REST API debug log doesn’t offer any clues, you can try disabling plugins one by one to see if that resolves the issue. You can also try using a different browser to rule out browser-specific issues.

What are some common plugin conflicts that could cause this error?

Plugins that modify the WordPress core, such as those for caching, security, or optimization, are often culprits. Plugins that add custom features, such as contact forms or social media integration, can also create conflicts.

Is there a way to check for mixed content errors on my website?

Yes, you can use browser developer tools to check for mixed content errors. Open your website in a browser, right-click anywhere on the page, and select “Inspect” or “Inspect Element.” Go to the “Console” tab, and you should see any mixed content errors listed there.

Can I fix the invalid JSON error by simply clearing the cache?

Clearing the cache might help, but it’s not a guaranteed solution. It’s usually a good idea to clear the cache after making changes to your website, but if the error persists, you’ll need to investigate further.

What if I’m not comfortable editing the .htaccess file?

If you’re not comfortable with code, contact your hosting provider or a WordPress expert. They can help you regenerate or modify the .htaccess file safely.

Should I disable all plugins at once or one by one?

Disabling all plugins at once is a quick way to check if a plugin is causing the error. If the error disappears, you can then reactivate them one by one to identify the culprit.

Can I use the Classic Editor permanently?

While you can use the Classic Editor permanently, Gutenberg is the future of WordPress editing. It’s a more modern and user-friendly editor with many features. If you’re comfortable using Gutenberg, it’s generally recommended to stick with it.

If you’re interested in learning more about tech news, feel free to visit my website: www.naveedahmed.me.