Sesame Street Google is working on an alternative ad tracking system that could replace cookies, according to USA Today. The new system is called "AdID," and it would offer certain privacy and security enhancements over the cookie.

Cookies are little bits of code that advertisers and web sites drop into your browser as you surf the web. They track your web history, which advertisers use as a guide to your potential shopping interests.

Google has been slowly losing a war over the use of third-party cookies to track users on behalf of advertisers. You can see how gritty that was has become in this interview with executives from Mozilla, which makes Firefox.

Competing companies have lined up against cookies: Microsoft has made "do not track" the default setting in its Internet Explorer browsers. Apple's Safari browser blocks third-party cookies altogether. New versions of Firefox will block them, too. Part of the problem is that browser makers have very little financial incentive to maintain a robust cookie environment, and a much bigger financial incentive to make browsers that people love and trust.

Google's Chrome browser stands alone in allowing all cookies as the default setting. Chrome is now the most popular browser, but it easy to switch tracking off.

AdID would allow Google to abandon the cookie system altogether in favor of something that advertisers prefer, and thus skirt the cookie war.

If Google could prove that AdID was more useful for advertisers and more private for users than cookies, it could start a gold rush (in Google's favor) to use AdID.

It would also put Google's AdID in competition with Apple's cookie-substitute, the "identifier for advertisers" (IDFA or IFA). That cookie alternative is the default tracker on Apple's mobile devices running the new iOS 7 operating system.