When extensions show, an ad is more prominent and, typically, performs better—that is, more people click on it. The quality of your ad and the strength of your bid can affect whether or not your extension shows.

This article explains when and where extensions show. For tips, go to Make your extensions more likely to show.

Availability

Extensions appear with ads on the Search Network. Some extensions might also appear with ads on the Display Network. International availability depends on each extension type. For more information about each extension type, see Select extensions to use.

Factors determining when they show

AdWords shows your extensions depending on a number of factors such as:

• Your Ad Rank, which combines your bid, the quality of your ad and landing page, Ad Rank thresholds, context of the person’s search, and expected impact of extensions and other ad formats. AdWords requires a minimum Ad Rank (factoring in your extensions) before showing extensions. So, you may need to increase your bid or your ad quality (or both) in order for your extensions to show.
• The position of your ad on the Google search results page. There’s a limited amount of space available above Google search results for ad extensions, and ads in higher positions get the first opportunity to show extensions.  Ads in lower positions generally won’t have more extensions than ads in higher positions. Plus, the AdWords system generally won’t allow ads in lower positions to get more incremental clicks from extensions than the incremental clicks they’d get from moving up to a higher position. To show ads in higher positions, generally you need to increase your ad quality, bid, or both. Learn more About ad position and Ad Rank.
• Other extensions you’ve enabled. In each auction, we'll generally show your highest performing and most useful combination of eligible extensions and formats. You will not be able to get a combination of extensions which gives more expected click-through-rate (CTR) than the expected CTR of a higher ad position.

* Nguồn: Google