What is the DoubleClick DART cookie?
The DoubleClick DART cookie is used by Google in the ads served on publisher websites displaying AdSense for content ads. When users visit an AdSense publisher's website and either view or click on an ad, a cookie may be dropped on that end user's browser. The data gathered from these cookies will be used to help AdSense publishers better serve and manage the ads on their site(s) and across the web.
Google's use of the DART cookie enables it to serve ads to your users based on their visit to your sites and other sites on the Internet.