Top Smartphone Apps of 201512/23/2015December 23, 20151. Facebook (126m users) | 2. YouTube (97m users) | 3. Facebook Messenger (96m users) | 4. Google Search (95m users) | 5. Google Play (89m users) | Source: Nielsenhttps://p.dw.com/p/1HSUbImage: picture alliance/ZB/PedersenAdvertisement