what is crossdomain cookies? are they really useful ? if so when is it used

What is a crossdomain cookie ?

what are they meant 开发者_Python百科for ?

Can you give some senarios where crossdomain cookies are useful. Would appreciate for in depth explanation.

Are you referring to accepting cookies from other sites? These are usually disabled in modern browsers, which only accept cookies from the site whose address is in address bar and not others.

The reason they were banned was they made trivial to track users between collaborating websites, although the advantage provided by this banning is dubious (there are equally effective methods available).

Note that a website can also define a cookie whose scope is larger than the current domain, as long as it doesn't ascend to a top-level domain. For instance meta.stackoverflow.com could define a cookie whose scope included whatever.stackoverflow.com and even stackoverflow.com, but not example.com.

Cross domain cookies are cookies that can be read by website code running on different domains. They are very useful for tracking user behavior and otherwise violating people's privacy, so don't use them!