A Cross-domain Cookie

Because every cookie that is set has a domain associated with it, every cookie belongs to one specific domain. The browser keeps the cookies for each domain separate so they cannot be shared.

Until Cross-domain Cookie.

Cross-domain Cookie

The Cross-domain Cookie system emulates behavior suggesting a cookie is being used at more than one domain.

What actually happens is that the cookie is set at one domain (the remote domain) — just like normal. With the Cross-domain Cookie system, a second domain (the local domain) obtains the value of that remote domain's previously-set cookie and sets the cookie locally for itself.

As an example of use, perhaps you have a domain where you have special files people can download. They have to register and log in to download the files. When they log in, a cookie is set in the browser.

Let's call that domain exampledownload.com

Now, let's say you have a second domain with a help center. Instead of people having to register again and log in again, you want to just use their login cookie from exampledownload.com.

The Cross-domain Cookie system lets you do that.

All the software needed to create a Cross-domain Cookie system for your own websites is available in the member area. (Log-in required.)