Publishing Failed: The Response Is Not a Valid JSON Response — Fix It Fast

If you’re trying to publish a post in WordPress and see:
“Publishing failed. The response is not a valid JSON response.”
this means something is blocking WordPress REST API. Here are the quickest ways to fix it.

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1. Refresh Your Permalinks

This solves the issue most of the time.

1. Go to Settings → Permalinks
2. Click Save Changes (don’t edit anything)

WordPress rebuilds .htaccess and fixes the broken routes.

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2. Fix Wrong Site URLs

If your Site URL and WordPress URL don’t match, WordPress returns invalid JSON.

Go to:
Settings → General

Make sure both are identical:

https://yourdomain.com

No “www.” mismatch, no http/https mismatch.

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3. Disable Security Plugins Blocking REST API

Security plugins often block REST requests.

Temporarily disable:

• WordFence
• WP Cerber
• iThemes Security
• Hide My WP
• Limit Login Attempts

Try publishing again. If it works, reactivate plugins one by one to find the culprit.

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4. Cloudflare Block or Rocket Loader Issue

If your site uses Cloudflare, two things can break JSON response.

A. Firewall Blocking REST API

Go to: Cloudflare → Security → Events
If REST URLs are blocked → allow them.

B. Disable Rocket Loader

Go to: Speed → Optimization
Turn Rocket Loader → OFF

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5. Fix Mixed Content (HTTP/HTTPS Conflict)

If some assets load over HTTP and some over HTTPS, JSON breaks.

Quick Fix

Install Really Simple SSL and let it fix everything automatically.

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6. Plugin or Theme Conflict

Something might be breaking REST routes.

Steps:

1. Disable all plugins
2. Try publishing
3. If it works → reactivate plugins one by one
4. If not → switch to a default theme (Twenty Twenty-Four) and test

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7. Hosting ModSecurity Blocking Editor

Some hosting providers have strict ModSecurity rules.

Ask your hosting support:
“Please whitelist ModSecurity rules blocking WordPress REST API for my domain.”

Or turn off ModSecurity from cPanel if allowed.

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8. Incorrect .htaccess File

A corrupted or altered .htaccess can cause this.

Default 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

Replace your existing one if needed.

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