WordPress 5.3 release failed. Error message: This response is not a valid JSON response.

Today, a website owner friend in the group reported that after upgrading to WordPress 5.3, when publishing a post, it prompts:Publish failed. Error message: This response is not a valid JSON response.

Common situations of WordPress post publishing failure

The occurrence of this problemusually has two reasons： 1. Plugin and editor compatibility issues 2. WP REST API issues 3. System image reasonsBelow, we analyze the solutions to these two types of problems.

Plugin and editor compatibility issues

This issue usually appears with the Gutenberg editor; it may be that a plugin you installed has compatibility issues with the Gutenberg editor. Simply disable the Gutenberg editor and test again. Disabling method:How to Disable the New Gutenberg Editor in WordPressAdditionally, some users reported that switching to Firefox browser allows normal publishing; you can also try this.

WP REST API issues

If you use the browser's F12 feature to inspect resources when publishing a post, you will find that WP REST API reports an error. At this time, you can try disabling WP REST API to test if it works normally. To disable WP REST API, you can install the following plugin.Disable WP REST API

System image reasons

The user who reported this issue to Naiba finally found through testing that it was a bug in the system image. Reinstalling the website environment with a different system image and then installing the website resolved it. It should be caused by a component in the system image being incompatible with the new version of WordPress. For technical novices, it's more troublesome to figure out the exact problem, so it's faster to just change the image.

Indirectly solve the problem by inserting via Media Library

Some users have reported that if your WordPress upload file promptsThis response is not a valid JSON response. Then, when uploading images, you can click on the Media Library, and then from theMedia Libraryinterface, click theUpload buttonto upload. Do not directly click the upload button in the Post interfaceto upload image files, which canindirectly resolvethis error.  

The above methods didn't work?

If neither of the above common situations applies to you, you can also use the following methods to diagnose and troubleshoot the issue.

1. Disable all plugins and switch themes to try
2. Reinstall WordPress to try

If you have already tried disabling plugins, switching themes, and reinstalling WordPress, and still cannot resolve the issue, you can only refer to the ultimate solution below.

• Solution for WordPress 5.3 Image Upload and Post-Processing Failure: Resize to 2500 Pixels
• Solution for Forcing WordPress Image Uploads to be Cropped to 2560 Pixels

If you have checked that the server folder permissions are normal and still cannot publish posts, then you can only try reinstalling the website environment (for safety, you can first install a WordPress on another server to test if it works normally).

Are you experiencing WordPress update failure?

Some friends may also encounter WordPress update failure promptsThis response is not a valid JSON response. In this case, manually updating solves the problem. There are two related articles you can check out.

• WordPress 429 Too Many Requests Error: Methods for Updating Themes and Plugins
• Manual Plugin Update_Method for Manually Upgrading WordPress Plugins
• Several Methods for Automatic and Manual WordPress Updates