Cyber Monday up 18.7 pct.
That growth in sales follows a disappointing weekend in brick-and-mortar stores.
Millions of Americans took advantage of online deals ranging from free shipping to hundreds of dollars off electronics and half-price clothing Monday, which was expected to be the busiest online shopping day of the year.
The spending surge on so-called Cyber Monday came after a disappointing holiday weekend in stores. And it showed that Americans are increasingly comfortable buying items on tablets and smartphones.
Early results showed online shopping was up 18.7 percent compared with the same time last year, according to figures by IBM Benchmark. Mobile traffic, which includes smartphones and tablets, accounted for 30 percent of all online traffic.
"I haven't shopped for a Christmas present in a store in three years," he said, making purchases from his iPad instead. "It's a lot more convenient to be at home and shop."
The National Retail Federation, a trade group, predicts more than 131 million people will shop online Monday, up about 2 percent from last year. Meanwhile, UPS expects to pick up more than 32 million packages on Monday, about a million more than Cyber Monday last year.
And research firm comScore expects Cyber Monday sales of $2 billion, up from about $1.47 billion last year. Online sales account for about 10 percent of total holiday spending, which is expected to grow about 3.9 percent to $602.1 billion for the months of November and December.
Joel Anderson, president and CEO of Walmart.com, said he anticipates Cyber Monday to be the site's busiest day ever. He said 2013 is the "tipping point" for mobile traffic, which includes smartphones and tablets.
More than half of Walmart.com's traffic came from smartphones and tablets on Thanksgiving and Black Friday, Anderson said. And he expected the same to be true on Monday.
He said "2013 is the year online went mobile."
Cyber Monday comes after retailers' failed efforts to boost spending during the holiday weekend. They offered big discounts in early November, and several opened stores on Thanksgiving. But the retail federation predicts that spending fell for the first time ever, down 2.9 percent to $57.4 billion, during the four days that ended Sunday.