A simple, static, passive (CDN-compatible) way of checking if third party cookies are enabled in a browser. Consists of two scripts - one that will set a cookie (start.html), and another that will post a message depending on if the cookie is present or not (complete.html).
Deploy the two scripts somewhere on a different domain from the main application, then load them using check.html.
Thanks to github pages, the scripts are hosted already at https://learningscience.github.io/3rdpartycookiecheck/start.html -- so you can use that as a live version. For production, it's better to deploy somewhere under your control.
To see the client code in action, run this JSFiddle: https://jsfiddle.net/tugawg8y/
- Cookie renamed
- Message renamed
- Moved example code into check.html
- Added timeout that sets third part cookies as unsupported after 10 seconds if no message is received from complete.html