The error "Request header field Access-Control-Allow-Headers is not allowed by itself in preflight response" arises when a preflight (OPTIONS) request, sent to check if a cross-origin request is safe, doesn't explicitly list all the custom headers the actual request will use in the Access-Control-Allow-Headers response header. This means the server needs to be configured to allow the specific headers being used in the actual request. Resolve in Framework / core level in Server side handle option request and return with header. Header always set Access-Control-Allow-Origin "*" Header always set Access-Control-Allow-Methods "*" Header always set Access-Control-Allow-Headers "*" Resolve in Server level change in .htaccess file <IfModule mod_headers.c> <If "%{REQUEST_METHOD} == 'OPTIONS'"> Header always set Access-Control-Allow-Origin "*" Header always set...