NetworkError: Failed to execute 'send' on 'XMLHttpRequest'

Question

I\'m trying to do a POST ajax request to a server hosted locally on my laptop but I can\'t seem to get any information back. When I click a button on my site (localhost), I

Answer 1

I was having the same problem, with an identical error message. In my case it was caused by the server setting a Feature-Policy header with sync-xhr: none. Removing this directive fixed the problem.