Originally published: November 20, 2023 · Last updated: August 13, 2026
The WordPress message “The response is not a valid JSON response” usually appears when the block editor expects data from the WordPress REST API but receives an unexpected response.
The message is generic. It does not necessarily mean that your article contains bad JSON. More often, WordPress is having trouble communicating correctly between the editor and the site.
Why this happens
The block editor relies on the REST API to load and save content. If that communication is interrupted, redirected or misconfigured, WordPress may show the JSON error instead of a more specific explanation.
1. Check Site Health
Open Tools → Site Health. WordPress includes checks for the REST API, HTTPS and other communication features. If Site Health reports a problem, start there rather than changing the post itself.
2. Confirm the site uses one consistent URL
Check the WordPress Address and Site Address under Settings → General. On an HTTPS site, both should normally use the intended HTTPS domain. URL mismatches can prevent editor requests from reaching the expected destination.
3. Save the permalink settings once
Open Settings → Permalinks and save the current structure without changing it. This refreshes WordPress rewrite rules and can solve some routing-related editor problems.
4. Clear the relevant caches
If your site uses a WordPress cache plugin, hosting cache or CDN, clear the caches after checking the settings above. Old cached responses can sometimes keep an already-corrected problem visible.
5. Review recent changes
If the error started immediately after a plugin, theme or configuration change, that change is an obvious candidate. Test changes on a staging copy when possible rather than experimenting on a busy production site.
6. Test for a plugin or theme conflict
On staging, temporarily switch to a standard theme and disable non-essential plugins in a controlled sequence. If the editor begins working again, re-enable items one at a time until the conflict is identified.
Do not keep repeating the same save operation
If WordPress cannot complete the request correctly, repeatedly clicking Update rarely solves the root problem. Stop, check Site Health and the site configuration, then test again after one controlled change.
A practical troubleshooting order
- Run Site Health.
- Verify the site URLs and HTTPS.
- Save the current permalink settings once.
- Clear caches.
- Review the most recent site changes.
- Test plugins and theme on staging if necessary.
The key point is simple: the JSON message is usually a symptom of a WordPress communication problem, not a content-format problem.
Official references: WordPress REST API Handbook and WordPress Site Health.