How to Fix “Updating Failed. The response is not a valid JSON response” in WordPress (2026 Working Method)

It happens to the best of us.

You just finished writing a killer blog post. You hit that blue “Update” or “Publish” button, expecting to see the success message. Instead, a red banner pops up at the top of your editor:

“Updating Failed. The response is not a valid JSON response.”

Heart rate goes up, right? I’ve been there. Just yesterday, I was migrating a client’s site, and this exact error froze my workflow.

Here is the good news: Your site is not broken, and you haven’t lost your content.

This error usually happens when the Block Editor (Gutenberg) tries to talk to the server, but something blocks the conversation. It’s like trying to make a phone call, but the line is dead.

In this guide, I’ll walk you through the exact steps I use to fix this error. We will start with the easiest fix (which works 90% of the time) and move to the technical ones if needed.

Let’s get that green “Published” button back.

Method 1: The “Magic” Fix (Resave Permalinks)
Before you touch any code or deactivate plugins, try this. It sounds too simple to be true, but it fixes this JSON error for almost everyone.

Sometimes, your WordPress permalink structure gets out of sync, especially after a migration or a major update.

• Go to your WordPress Dashboard.
• Navigate to Settings > Permalinks.
• Scroll down to the bottom. Do not change anything.
• Just click the “Save Changes” button.

Now, go back to your post and try to save it again. Did it work? If yes, you are done! If not, let’s check the next culprit.

Method 2: Check Your Site URLs (The SSL Mismatch)
This is a very common issue in 2026, especially if you recently added an SSL certificate (moved from HTTP to HTTPS).

If your site files are loading over HTTPS but your dashboard settings still say HTTP, the Block Editor will fail to send JSON data. This creates a “Mixed Content” error.

How to check:

• Go to Settings > General.
• Look at the WordPress Address (URL) and Site Address (URL).
• Make sure both start with https://.
• If one says http:// and the other says https://, correct them to match.

Pro Tip: If these fields are greyed out (you can’t edit them), it means they are hardcoded in your wp-config.php file. You might need to check your hosting file manager.

Method 3: The “.htaccess” File Fix
If the permalink trick didn’t work, your server’s .htaccess file might be corrupted or misconfigured. This file controls how your server handles requests. If it’s broken, the JSON response gets blocked.

• Don’t worry, we are just going to regenerate it.
• Connect to your site via FTP or use the File Manager in your Hosting Control Panel (cPanel/hPanel).
• Find the .htaccess file in your root folder (usually public_html).
• Backup: Download a copy of it to your computer (just in case).
• Delete the file from the server.
• Now, go back to your WordPress Dashboard > Settings > Permalinks and click “Save Changes” again.

WordPress will automatically generate a fresh, clean .htaccess file for you. Try saving your post now.

Method 4: The REST API Conflict (Security Plugins)
The Gutenberg editor relies heavily on the WordPress REST API to save posts. If you have a security plugin (like Wordfence, iThemes) or a Firewall (like Cloudflare) set to “High,” it might mistake the editor’s request for a malicious attack and block it.

How to test this:

• Temporarily deactivate your security plugin.
• Try to save the post.

If it works, you know the culprit. You don’t need to delete the plugin; just check its settings to “Whitelist” your IP address or the REST API.

Method 5: Still Not Working? Switch to the Classic Editor
If you are on a tight deadline and need to publish this post right now despite the error, here is a quick workaround.

• This isn’t a permanent fix, but it will let you publish your content.
• Go to Plugins > Add New.
• Search for “Classic Editor”.
• Install and Activate it.

The Classic Editor doesn’t use the JSON/REST API method to save posts, so it bypasses the error completely. You can publish your article, and then troubleshoot the main issue later when you have more time.

Final Thoughts
The “Response is not a valid JSON response” error looks scary, but it’s usually just a small misconfiguration. For most of my clients, Method 1 (Resaving Permalinks) is the silver bullet.

Did one of these methods work for you? Or did you find a different trick? Let me know in the comments below—it might help someone else save their day!