Ad extensions are additional pieces of information about your business, like a phone number or a link to a specific page on your website, you can add to your ads. Ad extensions are free to add to your ads, with the usual charges for any clicks you get. Including ad extensions can improve the visibility of your ads, which can lead to more clicks and improve your ROI. There are many types of ad extensions available in Microsoft Advertising: App Extensions, Call Extensions, Callout Extensions, Image Extensions, Location Extensions, Price Extensions, Review Extensions, Sitelink Extensions, and Structured Snippet Extensions. For more about ad extensions, see the About ad extensions help article.
Ad extensions are stored in a shared library at the account level. After adding the extension to your shared library, you must also explicitly associate it with the account or one or more campaigns or ad groups within the account for the extension to become eligible for delivery. For more details on associating ad extensions, see Managing Ad Extensions with the Bulk Service and Managing Ad Extensions with the Campaign Management Service in the sections below. For ad extension association limits per entity, please see Entity Limits for Ad Extensions.