Third party cookie check for browsers

A simple, static, passive (CDN-compatible) way of checking if third party cookies are enabled in a browser. Consists on an script that will set a cookie, and post a message depending on if the cookie is present or not.

Deploy the scripts somewhere on a different domain from the main application, then load them similar to the example below:

<body>
  <script>
    var receiveMessage = function (evt) {
      if (evt.data === 'third-party-cookies-enabled') {
        console.log('thid party cookies are not supported');
      } else if (evt.data === 'third-party-cookies-disabled') {
        console.log('thid party cookies are supported');
      }
    };
    window.addEventListener('message', receiveMessage, false);
  </script>

  <iframe src="LOCATION_OF_THE_SCRIPTS/start.html" style="display:none" />
</body>

It's also a good idea to set up a timeout that will automatically label third party cookies as unsupported if no recognised event comes back after a while, just in case network fails.

Live example

Thanks to github pages, the scripts are hosted already at https://jonidelv.github.io/third-party/start.html -- so you can use that as a live version. For production, it's better to deploy somewhere under your control.

jonidelv/third-party

Third party cookie check for browsers

Live example