Google make protecting privacy a priority by being clear about what information they collect and how they will use the information to show relevant ads, and by offering choices to consumers about what information to share with them. They make it easy to opt out of cookie-based advertising for those who wish to do so. They will not collect, sell, or share personal information from ad serving cookies without your explicit consent.

Google, Third party cookies and Opting Out

What information does Google use to serve ads when I do searches on Google or surf on websites that are part of the Google content network?
Google serve ads on their own websites through their AdWords program and on websites in the Google content network through their AdSense program. Google use a variety of methods to deliver ads that are relevant. One is using context. If you search for "golf" on our search engine, you'll see golf-related ads. If you visit a gardening site, ads there may be related to gardening.

Google also make ads geographically relevant, which they do with the help of IP addresses. If you're in Boston searching for cab companies, you probably want ads for Boston-based, not London-based cabs. Google also use cookies, which help serve ads in the right language and limit the number of times you see the same ad.

How does Google use cookies to serve ads?
A cookie is a snippet of text that is sent from a website's servers and stored on a web browser. Like most websites and search engines, Google uses cookies in order to provide a better user experience and to serve relevant ads. Cookies are set based on your viewing of web pages in Google's content network and do not contain any information that can identify you personally. This information helps Google deliver ads that are relevant to your interests, control the number of times you see a given ad, and measure the effectiveness of ad campaigns. Anyone who prefers not to see ads with this level of customization can opt out of advertising cookies. This opt-out will be specific only to the browser that you are using when you click the "opt out" button.

How does Google use DoubleClick cookies to serve ads?
Google uses the DoubleClick DART cookie on our Google content network to serve more relevant ads across the web and limit the number of times you view an ad. When you visit a website and view an ad or click on an ad supported by Google's advertising services, we may set a cookie on your browser. This advertising cookie will appear in your browser as .doubleclick.net.

When the cookie is set on your browser, it allows Google to gather information about your browser's interaction with a given ad. This information gets recorded in a log that looks something like this:

The "time" field reflects the time the ad was displayed. The "ad placement id" and "ad id" identify the advertising campaign and the specific ad served. The "userid" is the display ad cookie that identifies the browser. The "client IP" reflects the user's Internet Protocol (IP) address. A "referral URL" indicates the URL of the page where the ad was served. Our logs also record whether a user's browser clicks on or interacts with an ad.