Android has the largest mobile OS usage by share, based on ad impressions, with iOS coming in second and BlackBerry in third, according to the latest “Mobile Mix” report from Millenial Media (http://www.millennialmedia.com/), a mobile advertising platform.

Android has 56% of the connected device and smartphone OS mix; Apple came in second with 28% for iOS. However, Apple takes the top spot for ad impressions among all manufacturers, with 23.5% of impressions among the top 15 device manufacturers and 12.53% of the top single-device impressions going to the iPhone.

Appleā€™s share grew slightly compared to the third-quarter results. The company also continues to take a big chunk of mobile advertising spending (40%) compared with Android (50%).