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WordPress Publishing Error

 — #WordPress


Recently while working on a WordPress project with Ups Dock, I encountered a weird error where I wasn't able to update or publish a simple post in my local WP admin.

It looked something like this:

Draft fail

Sometimes the error message would be slightly more helpful: Publishing failed. Error message: The response is not a valid JSON response.

Publish error

And if I popped open the console, I saw these errors:

Console errors


Since the error message had to do with a JSON response, I initially thought it was a Gutenberg or ACF issue. But it turned out this was happening because I was on the https WP admin (i.e., not the unsecure WP admin (

It was a CORS error!! I was trying to modify a non-https domain from a https domain. Switching to a non-https WP admin allowed me to publish posts with no problem.