An ad unit is a space set aside in an application or web page where ads will appear. Ad units can contain one or more ads, and are available in many different formats. Ad units can be constrained to their borders or can expand to display more content to the user.

Microsoft pubCenter allows you to define many ad unit settings on the server side. Set up style attributes, keywords, and reporting information within pubCenter, and the software keeps track of the data for you. When you update your global ad exclusions or reporting channels, you only have to save it once (in pubCenter), instead of having to re-save it on every page where you display ads.

Ad unit code is the code that you insert into your web site or application to enable advertising from pubCenter. After you create an ad unit in pubCenter, the ad unit code is automatically generated for your use. You must then add it to your web pages or applications. If you are creating a mobile application, your users will need to update through the marketplace before they can begin to receive ads.

Available ad units include Windows Phone and Windows 8 content ads, text-based Search ads, Display ads including graphics and video, and more.