Which was the most popular smartphone app in the United States during 2015? If you guessed Facebook, you’d be correct.

According to Nielsen estimates, the Facebook app notched more than 125 million average unique users per month during 2015. It was an ~8% increase in the app’s user volume over the previous year.

The second most popular smartphone app was YouTube, but at fewer than 100 million, its average unique user volume was substantially lower than Facebook’s.

The Nielsen estimates are calculated based on a monthly survey of 30,000+ mobile subscribers age 13 and older in the United States, as well as a panel of ~9,000 English-speaking adults (age 18+).

Here is Nielsen’s “Top Ten” chart for the most popular smartphone apps in 2015:

• Facebook app: ~127 million average unique monthly users

• YouTube: ~98 million

• Facebook Messenger: ~96 million

• Google Search: ~95 million

• Google Play: ~90 million

• Google Maps: ~88 million

• Gmail: ~75 million

• Instagram: ~56 million

• Apple Music: ~55 million

• Apple Maps: ~47 million

Within the top ten list, the two apps with the highest user growth in 2015 were Facebook Messenger, which charted an increase in average monthly users of ~31%, and Apple Music, with ~26% growth.

Also noted by Nielsen, the level of smartphone penetration ticked up yet again in 2015, so that today four out of five mobile subscribers are using a smartphone rather than a feature phone.

As for the ongoing competition between Apple and Android for smartphone hegemony, it remains a real donnybrook but with Android ahead.

As of Q3 2015, Android devices represented ~52.5% of the subscriber base whereas ~42.5% of Americans used Apple iOS devices to access their apps.  (The remainder is made up of Blackberry users and phones operating on Windows.)

Additional information about the Nielsen evaluation and analysis can be viewed here.  It will be interesting to see how these trends might change in 2016.  Would anyone care to make any predictions?