I think some of the comments re: browser agent are missing the point. I think the poster was not focused on whether it can identify the system or browser type,

I think some of the comments re: browser agent are missing the point. I think the poster was not focused on whether it can identify the system or browser type, but instead as a technique to provide a potentially unique (or somewhat unique) fingerprint that a user can't eliminate easily. So, a site could use this code (along with other techniques) to identify your browser and even if you delete a set cookie, detect that it's the same browser. They may discover, btw, that it's not as unique as they think it is, but combined with other techniques, can be a tracking attribute that is difficult to disable. It doesn't seem resilient to change in the underlying system from my cursory view (if I change my graphics card, resolution, or color depth, does this id change?) but like https://panopticlick.eff.org/ https://panopticlick.eff.org/, it's useful and a good cautionary tale to see the variety of ways your browser can be uniquely distinguished, with and without the use of cookies. BTW, the icons on the left side of the browserleaks page are actually a menu and offer other "leaks" of info from the browser: some well known, others more subtle.