6 Solutions to the problem “the response is not a valid JSON response” WordPress Error

You’re working in the WordPress editor, but the document isn’t updating. In fact, you receive an error message stating, “Updating failed.” “The response is not a valid JSON response,” says the error message. Before you panic, let me assure you that this error is easily rectifiable so that you do not lose your hard work.

This is one of the most common WordPress errors that users experience on their sites.

Why does “the response is not a valid JSON response” error occur?

There could be multiple reasons why this error occurs. This post delves into each reason and offers multiple solutions to solve the problem.

Before you try anything else, you should try resetting your permalinks to resolve the invalid JSON response error. Navigate to Settings > Permalinks in your WordPress dashboard. Then ensure that the correct permalink setting is selected and click the Save Changes button.

Now try updating a page. The error should be fixed but if it still occurs, try out the solutions below.

2. Disable the Block editor and switch back to Classic editor

WordPress classic editor
Old is still Gold in WordPress

The error “Updating failed. Error message: The response is not a valid JSON response.” is overwhelmingly seen in the new Block editor called Gutenberg.

The easiest way to resolve the updating error is by disabling Gutenberg and switching back to the Classic editor. As they say, old is Gold.

You can install the Classic Editor plugin for this. Once you have activated the plugin, try to save your posts. You should not see any error message now.

But what if you still want to use the block editor?

Nice question. It could be that reverting to the classic editor is not an option for you. In that case, you should follow what we are doing on PassionWP. With the classic editor plugin installed and activated, navigate to Settings>Writing.

Now select the Classic Editor as the “default editor for all users” option, save your changes, and clear your website cache. Right after this, select the Block Editor as the default editor and again save the changes.

Now try editing an existing post or create a new post with the block editor. You should not encounter the JSON response error. However, it could be that the editor fails to automatically save your changes.

In this event, press Ctrl + S (Cmd + S for Mac) to manually save your changes. This solution works for us and we are using the block editor without encountering the JSON response error.

3. Mixed content error due to the use of SSL certificate

Another common reason for this error is the use of a secure socket layer (SSL) certificate (HTTPS) on your WordPress site. Using an SSL certificate can result in some content being delivered non-securely on HTTP protocol even while the rest of the content is delivered in a secure manner over HTTPS protocol.

This results in a mixed content error in which both https and https content is transmitted at the same time to the web browser, usually Google Chrome.

How to solve the Mixed Content Error in WordPress?

We investigated the mixed content error and noticed that it is linked to the use of the Really Simple SSL plugin that is used by over 3 million WordPress users to configure HTTPS on their websites.

To resolve the “the response is not a valid JSON response” or mixed content error, navigate to Settings > SSL. This will open the plugin’s settings. Now click on the Settings tab.

You should do the following two things here:

  1. Ensure that the “Mixed content fixer” option is turned on. This prevents mixed content problems on your website that we discussed above.
  2. Next, you should turn on the “Use an alternative method to fix the mixed content” option. This will ensure that “the response is not a valid JSON response” error does not erupt abruptly while editing.
How to fix the response is not a valid JSON response error in WordPress
Really Simple SSL settings

After saving the changes, go back to the post you were working on and try saving your post or page. You should no longer experience the response is not a valid JSON response error.

4. Plugin conflict

The more plugins you use on your WordPress site, the higher the chances of conflict between plugins. Some of these conflicts can result in invalid JSON response errors as well.

I have witnessed this issue on websites running a high number of plugins, say more than 40. But it’s not just the number of plugins that matter. Rather, some plugin files might be causing the JSON bug on your website.

For instance, on a client’s site, the Yoast SEO plugin was causing the JSON response error.

So, in order to rule out any plugin conflict, you should deactivate all the plugins on your website. If required, use the Health Check and Troubleshooting plugin to deactivate the plugins in the backend while the front end remains the same for your visitors.

If the JSON response error disappears when you deactivate all the plugins means that one of the plugins was causing the error. Now, you should activate the plugins one by one. If the error recurs on activating a particular plugin implies that this plugin was the culprit.

5. WordPress REST API conflict

The WordPress admin backend uses the REST API to communicate with the server. If there is any conflict with this API, WordPress won’t be able to connect with the server and will instead display the JSON response error.

In order to identify if the REST API problem is indeed causing the problem, try editing one of your posts and saving it. Once the invalid JSON error is displayed, right-click the mouse button and then click Inspect to open Chrome’s dev tools.

Now under the Console tab, check whether any REST API error is displayed. If it is, then the REST API conflict is indeed the cause.

The best solution to this is to contact your web host since REST API errors are mostly caused at the server level. If you’re using a cache plugin like LiteSpeed Cache, you should disable the setting to cache the REST API and try saving the post again.

6. Alternative solutions to the response is not a valid JSON response error

Deactivate all the plugins on your site and edit the content normally. If you’re using the Really Simple SSL plugin then deactivate this plugin first. Subsequently, try saving the document. If you are able to save it without facing any errors, re-activate the plugins one by one to check which plugin was causing the error.

There is another solution you can try to fix the response is not a valid JSON response error in WordPress.

Navigate to Settings > Permalinks. Change the permalink structure from post-name or the current structure to Plain i.e. https://yoursite.com/?p=123. Now try saving your post/page. The problem should have been resolved.

Fix the response is not a valid json response error by changing the permalink
WordPress permalinks settings

But try this solution if all other methods fail as changing the permalinks will result in huge SEO issues on a live website and you will also need to add multiple redirects.

We discussed 6 possible solutions to the response is not a valid JSON response error in WordPress. I hope one of these methods worked for you. If it did, let me know in the comments below. If it didn’t, post your specific problem so others can suggest different solutions.

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