Updating Failed. The Response is Not a Valid JSON Response
A Hidden Culprit
If you’ve ever encountered the “Updating failed. The response is not a valid JSON response” error while working on your WordPress site, you know how frustrating it can be. This error typically occurs when there’s a communication issue between the WordPress editor and the server, often due to problems with the JSON response format. In this article, we’ll explore common solutions to this problem and highlight a lesser-known culprit: The Duplicate Alt Text.
Understanding the Error
Before diving into the solutions, it’s essential to understand what this error means. WordPress uses JSON (JavaScript Object Notation) to communicate with the server when you update or publish content. If the server’s response is not in the expected JSON format, WordPress throws this error. This can happen for various reasons, including permalink issues, SSL misconfigurations, plugin conflicts, and more.
Common Solutions
- Refresh Permalinks One of the simplest solutions is to refresh your permalink settings. Navigate to Settings > Permalinks in your WordPress dashboard and click Save Changes without making any modifications. This action forces WordPress to update the permalink structure, which can resolve the error.
- Check Site URLs Ensure that your WordPress Address (URL) and Site Address (URL) match and are correctly configured, especially if you’re using SSL (HTTPS). Mismatched URLs can cause communication issues between the editor and the server.
- Deactivate Plugins and Themes Plugin or theme conflicts can also trigger this error. Try deactivating all plugins and switching to a default theme (like Twenty Twenty-One). If the error disappears, reactivate your plugins one by one to identify the culprit.
- Fix .htaccess File Issues with your .htaccess file can disrupt permalink settings. You can regenerate this file by renaming the existing one and letting WordPress create a new one by saving the permalink settings again.
- Check for Mixed Content Mixed content (loading both HTTP and HTTPS content) can interfere with the JSON response. Ensure all your site content is served over HTTPS.
The Sneaky Culprit: Duplicate Alt Text
While the above solutions are well-known, there’s a less obvious cause (at least for us!) that can also trigger this error: Duplicate Alt Text. If you have an image on the page you’re editing with an Alt text that matches another from another image, it can disrupt the JSON response format. This issue is less documented but can be a sneaky culprit.
Case Study
Recently, a user encountered the “Updating failed. The response is not a valid JSON response” error. The error was occurring only on one page, all the other pages were acting normal (not returning error while saving), except this one page. After trying all the common solutions without success, it became really annoying of why would this single page behave this way, they restored a copy of the website from a backup, and re-created the page from scratch, and even restored an older update where the plugins were not updated to the latest version, and yet the page was returning the same error. So the user took the trial-error approach, and they started to delete content from the page, section-by-section, and try to save after each deletion, and only after one of the images was deleted, the page saved successfully with no returning error. It was at that moment they discovered that the image on the page was the problem, and after checking the attributes, they realized that it had an Alt Text that is identical to another image that exists on the same page, even though they tried to add numbers after the original duplicate text, the error still persisted. Once they changed it completely, the error disappeared. This suggests that similar/identical strings in image Alt texts can interfere with the JSON response, causing the error.
How to Fix It
If you suspect that a long image title might be causing the error, follow these steps:
- Identify the Image Locate the image on the page you’re editing and reporting that error. Check the Alt Text attribute of the image.
- Change the Alt Text Edit the image and shorten the text. Ensure the Alt is unique and free of special characters that might disrupt the JSON format.
- Update the Page Save your changes and try updating the page again. If the error was due to the duplicate Alt text, it should now be resolved.
Conclusion
The “Updating failed. The response is not a valid JSON response” error can be frustrating, but with the right approach, it can be resolved. While common solutions like refreshing permalinks, checking site URLs, deactivating plugins, fixing the .htaccess file, and addressing mixed content issues are effective, don’t overlook other possibilities like long image titles causing the problem, sometimes the problem resides within one element or even the description of that element in one page only. By considering all potential causes, you can ensure a smoother editing experience in WordPress.
What’s Happening?
You try to save or update a post — and bam, this shows up:
“Updating failed. The response is not a valid JSON response.”
It means WordPress couldn’t talk to the server properly. Usually, it expected a clean message (in JSON format), but got something messy instead.
Quick Fixes (Try These First)
1. Refresh Permalinks
Go to: Settings → Permalinks
Click Save Changes (don’t touch anything else)
2. Check Your Site URLs
Make sure WordPress URL and Site URL are:
The same
Start with https:// (if you have SSL)
3. Disable Plugins & Themes
Deactivate all plugins
Switch to a default theme (like Twenty Twenty-One)
If it works, turn plugins back on one by one to find the problem
4. Reset .htaccess
Rename your
.htaccessfile to.htaccess-oldGo to Settings → Permalinks and click Save Changes to auto-generate a clean one
5. Check for Mixed Content
Make sure all your content is loading over HTTPS
No HTTP images or links sneaking in
The Unexpected Fix: Duplicate Alt Text
There’s a sneaky bug that’s not well-documented:
If two images on your page have the same “Alt Text”, WordPress might freak out and break the save function.
Yes — even if you just added a number at the end.
Real Example
A user had this exact error, but only on one specific page.
They tried:
Restoring backups
Downgrading plugins
Rebuilding the page from scratch
Nothing worked… until they started deleting parts of the page.
Guess what fixed it?
Deleting an image with duplicate Alt Text.
When they changed that Alt Text to something totally different, the error disappeared.
How to Fix It
Find the Image
Go to the page with the error
Check the images one by one
Edit Alt Text
Make sure each Alt Text is unique
Keep it short and simple (avoid symbols or long descriptions)
Save the Page
Try updating again
If the error vanishes, that was it!
Summary
This error has many possible causes — here’s your cheat sheet:
| ✅ Fix Attempt | Worth Trying? |
|---|---|
| Refresh Permalinks | ✅ Yes |
| Check Site URL/HTTPS | ✅ Yes |
| Disable Plugins / Theme | ✅ Yes |
Reset .htaccess | ✅ Yes |
| Check for Mixed Content | ✅ Yes |
| Check for Duplicate Alt Text | 🔥 Definitely |
If only one page is acting up, there’s a good chance the bug is hiding in just one image or text block.
