Is there any globaly unique identifier for a client machine accessible through the web browser?

Is there any way to identify a users machine through a browser without previously p开发者_StackOverflow社区utting cookies in? Probably no access to Mac Address through the web right? Just thought I'd ask...

There is no such identity element, and even if there were, the nature of the HTTP protocol would not prevent it from being spoofed.

In short: No.

This was partly why Intel tried to have unique processor IDs a few years back, but that didn't ever take off. (Which is good as now we have multi-core machines.)

Just install a cookie on the box. IP address is no good because of Natting. Someday we'll have IPv6 to do this correctly.

You could retrieve an IP address, but it frequently wouldn't mean much (if anything). If you retrieve the IP address the client is using, you'll get a whole lot of them that are 192.168.*. If you retrieve the address your server sees, it won't match that, and you might easily see several (possibly hundreds or even thousands) of machines with the 'same' IP address.

If you put those two together, you'll get something that's unique for the moment, but is subject to change at any time. The client's local IP address may change when their DHCP lease expires and their global IP address may change anytime they reboot their router (unless they have a static IP address, which you mostly don't have any way of knowing).