Facebook was the No. 1 app overall in 2013, but its photo-sharing subsidiary Instagram was the fastest-growing app among the top 10.
With an average of 103.4 million unique visitors last year between January and October, Facebook had easily the largest U.S. audience of any app, with traffic up 27% from 2012. But that growth rate paled in comparison to Instagram -- acquired by the social network in 2012 for $1 billion -- which saw its app audience surge 66% to 32 million last year, according to Nielsen data.
That’s partly a result of starting from a smaller base, but the comparison with Facebook won’t do anything to dispel the growing perception that the growth in social media -- especially among teens -- is shifting to single-purpose or messaging apps, including Instagram, Snapchat, Whatsapp, Whisper and others.
Instagram also outpaced Twitter, the No. 10 app that grew 36% to 30.7 million last year.