Google AdSense, commonly just AdSense, is an ad serving program run by Google. Website owners can enroll in this program to enable text, image and, more recently, video advertisements on their sites. These ads are administered by Google and generate revenue on either a per-click or per-thousand-impressions basis. Google is also currently beta-testing a cost-per-action based service.
How AdSense works
- In order to put ads on a web page, the webmaster inserts JavaScript code into the page.
- Each time a page with an AdSense tag is visited, the JavaScript creates an iframe and sets its "src" attribute to the page's URL.
- For contextual advertisements, Google's servers use a cache of the page to determine a set of high-value keywords. If keywords have been cached already, ads are served for those keywords based on the AdWords bidding system. More details are described in the AdSense patent.
- For site-targeted ads, the advertiser chooses the page(s) to display ads on and pays based on CPM (cost-per-thousand-impressions, or the price advertisers choose to pay for every thousand ads displayed).
- For referrals, Google adds money to the advertiser's account when visitors either download the referred software or subscribe to the referred service.
- Search ads are added to the list of results after a user preforms a search.
- Since the JavaScript is sent to the web browser when the page is requested, it is possible for other site owners to copy the JavaScript into their own web pages. To protect against this type of fraud, AdSense customers can specify the pages on which ads should be shown. AdSense then ignores clicks from pages other than those specified.
