Access-Control-Allow-Origin error sending a jQuery Post to Google API's

I solved the Access-Control-Allow-Origin error modifying the dataType parameter to dataType:'jsonp' and adding a crossDomain:true

$.ajax({

    url: 'https://www.googleapis.com/moderator/v1/series?key='+key,
    data: myData,
    type: 'GET',
    crossDomain: true,
    dataType: 'jsonp',
    success: function() { alert("Success"); },
    error: function() { alert('Failed!'); },
    beforeSend: setHeader
});

I had exactly the same issue and it was not cross domain but the same domain. I just added this line to the php file which was handling the ajax request.

<?php header('Access-Control-Allow-Origin: *'); ?>

It worked like a charm. Thanks to the poster

If you have this error trying to consume a service that you can't add the header Access-Control-Allow-Origin * in that application, but you can put in front of the server a reverse proxy, the error can avoided with a header rewrite.

Assuming the application is running on the port 8080 (public domain at www.mydomain.com), and you put the reverse proxy in the same host at port 80, this is the configuration for Nginx reverse proxy:

server {
    listen      80;
    server_name www.mydomain.com;
    access_log  /var/log/nginx/www.mydomain.com.access.log;
    error_log   /var/log/nginx/www.mydomain.com.error.log;

    location / {
        proxy_pass   http://127.0.0.1:8080;
        add_header   Access-Control-Allow-Origin *;
    }   
}

Yes, the moment jQuery sees the URL belongs to a different domain, it assumes that call as a cross domain call, thus crossdomain:true is not required here.

Also, important to note that you cannot make a synchronous call with $.ajax if your URL belongs to a different domain (cross domain) or you are using JSONP. Only async calls are allowed.

Note: you can call the service synchronously if you specify the async:false with your request.

try my code In JavaScript

 var settings = {
              "url": "https://myinboxhub.co.in/example",
              "method": "GET",
              "timeout": 0,
              "headers": {},
            };
        $.ajax(settings).done(function (response) {
          console.log(response);
            if (response.auth) { 
                console.log('on success');
            } 
        }).fail(function (jqXHR, exception) { 
                var msg = '';
                if (jqXHR.status === '(failed)net::ERR_INTERNET_DISCONNECTED') {
                    
                        msg = 'Uncaught Error.\n' + jqXHR.responseText; 
                }
                if (jqXHR.status === 0) {
                        msg = 'Not connect.\n Verify Network.';
                } else if (jqXHR.status == 413) {
                        msg = 'Image size is too large.'; 
                }  else if (jqXHR.status == 404) {
                        msg = 'Requested page not found. [404]'; 
                } else if (jqXHR.status == 405) {
                        msg = 'Image size is too large.'; 
                } else if (jqXHR.status == 500) {
                        msg = 'Internal Server Error [500].'; 
                } else if (exception === 'parsererror') {
                        msg = 'Requested JSON parse failed.'; 
                } else if (exception === 'timeout') {
                        msg = 'Time out error.'; 
                } else if (exception === 'abort') {
                        msg = 'Ajax request aborted.'; 
                } else {
                        msg = 'Uncaught Error.\n' + jqXHR.responseText; 
                }
                console.log(msg);
        });;

In PHP

header('Content-type: application/json');
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: GET");
header("Access-Control-Allow-Methods: GET, OPTIONS");
header("Access-Control-Allow-Headers: Content-Type, Content-Length, Accept-Encoding");