eBay on Wednesday reported mobile transaction volume on its platform more than doubled in 2012 to $13 billion, while mobile payments handled by its PayPal unit tripled to $14 billion. The mobile gains helped the e-commerce giant increase revenue 18% in the fourth quarter to $4 billion.

It posted earnings of $927 million, or 70 cents a share, beating analysts’ expectations by a penny.

eBay has been one of the biggest players in mobile commerce in recent years as more of its users complete transactions through its mobile properties.

"Mobile continues to rewrite the commerce playbook, and we continue to be a mobile commerce and payments leader," stated eBay president and CEO John Donahoe in its earnings release.

He added that he expects mobile payments through PayPal to surpass $20 billion this year. eBay only keeps a fraction of the billions in mobile purchases and payments transacted on its platforms. eMarketer projects U.S. m-commerce sales, across smartphones, tablets and other mobile devices, will reach $38.4 billion this year.

A Forrester forecast released today projects U.S. mobile payments--spanning in-store payments, remittances and m-commerce--will grow 48% annually from $18.2 billion in 2013 to $90 billion by 2017.