The trade body said that internet ad revenues of $42.8 billion were just ahead of broadcast TV on $40.1 billion, with the highest growth rate once again coming from mobile.
"The news that interactive has outperformed broadcast television should come as no surprise," said Randall Rothenberg, President and CEO, IAB. "It speaks to the power that digital screens have in reaching and engaging audiences," he added.
For the third year in a row, mobile achieved triple-digit growth year-over-year, rising 110% in 2013 to reach $7.1 billion. Mobile accounted for 17% of 2013 revenues, compared to 9% in in 2012.
Rothenberg said the "staggering growth of mobile" reflected the way smaller digital screens now played an integral role in consumers' daily lives. He also noted their "critical importance to cross-screen experiences".
Display-related advertising revenues had increased 7% to $12.8 billion, a figure which represented 30% of the year's revenues. And within that category, banner ads were the major format, accounting for 19% of all digital advertising but growing slowly at just 2.8%.
Digital video had grown more than twice as fast as display overall, at 19%, to a total of $2.8 billion; as a result, it also increased its share to become the fourth largest format, directly behind mobile.
Search remained the largest revenue-earning format, accounting for 43% of the total and bringing in $18.4 billion in 2013. This was a 9% rise on the previous year.
Retail advertisers continued to represent the largest category of internet ad spending, responsible for 21% in 2013, followed at some distance by financial services (13%) and automotive (12%).
"Our survey confirms that we are fully in transition to the post-desktop era," said David Silverman, Partner at PwC US, which prepared the figures.
He contrasted the triple-digit rate of mobile's growth with the mere 8% increase for traditional computer screens. "This is simply a reflection of the change in how and where consumers are viewing their information—on the go!" he stated.
Data sourced from IAB; additional content by Warc staff