'Publishing failed' means the editor couldn't save to your server, usually because a plugin, firewall or SSL issue blocked it. Your work is usually safe.
What it means
When you click Publish, the editor sends your content to the server via an AJAX request. If that request fails - plugin conflict, security rule, SSL mismatch, or server timeout - you get the error and your draft may not save.
Why it happens
The usual suspects are a security plugin blocking REST API calls, an SSL certificate issue causing mixed-content errors, a plugin conflict with the editor, or a server timeout on large posts.
A real example
A freelance writer could not publish posts for three days. Every hit on Publish ended with "Publishing failed. The response is not a valid JSON response." The cause was a security plugin blocking WordPress's REST API calls - the same API the block editor uses to save. Posts were not lost; they just could not save. Conflicts between security plugins and the REST API are one of the most common - and most misdiagnosed - publishing failures, because the editor gives no hint that a firewall is the reason.
What to do
- Check if your draft actually saved - look in Posts > All Posts for an autosave or draft version.
- Disable security plugins temporarily - many block REST API requests by default.
- Check browser console (F12) for the actual error - mixed content or CORS errors point to SSL issues.
- Try a different browser or incognito to rule out extensions.
- If posts are very large, the server may be timing out - try publishing in smaller chunks.
Still stuck? Publishing failures are frustrating but usually fixable - we can identify whether it's a plugin, SSL, or server limit and get you publishing again.
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