WordPress 'Updating Failed. The Response Is Not a Valid JSON Response'

How to fix it

Try these in order — the most common fix is first.

1. 1. Check the URLs

   1. Settings > General: WordPress Address and Site Address must both be correct and use the same protocol.
   Did this fix it? Yes No

2. 2. Reset permalinks

   1. Settings > Permalinks, click Save Changes without changing anything. If it persists, regenerate .htaccess by renaming it first.
   Did this fix it? Yes No

3. 3. Test plugins and theme

   1. Deactivate all plugins and switch to a default theme, then retry saving. Reactivate until the error returns.
   Did this fix it? Yes No

4. 4. Check redirects and firewall

   Copy steps
   1. Make sure only one thing forces HTTPS, and whitelist /wp-json/ in any firewall, CDN or security plugin rule.
   2. Open yoursite.com/wp-json/ in a browser. It should show JSON, not a page or error.
   Did this fix it? Yes No

5. 5. Use the Classic Editor temporarily

   1. Install the Classic Editor plugin to publish while you debug.
   Did this fix it? Yes No

Symptoms

When saving or publishing a post the editor shows 'Updating failed' or 'Publishing failed. The response is not a valid JSON response.'

Why it happens

• Mismatched WordPress Address and Site Address
• Broken permalinks or .htaccess rules
• A plugin or theme printing warnings or extra output before the JSON
• Mixed content or competing HTTPS redirects
• A firewall or security plugin blocking the REST API

This guide also covers

• updating failed the response is not a valid json response
• wordpress publishing failed json
• wordpress gutenberg updating failed

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• WordPress 500 Internal Server Error
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