The National Retail Federation, a trade group, predicted that more than 131 million people would shop online Monday, up about 2 percent from last year. Meanwhile, UPS expected to pick up more than 32 million packages on Monday, about a million more than on the same day last year.
Research firm comScore forecast 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 was projected to grow about 3.9 percent to $602.1 billion for the months of November and December.
Anderson predicted that Cyber Monday would be the site's busiest day ever.
More than half of Walmart.com's traffic came from smartphones and tablets on Thanksgiving and Black Friday. He expected the same to be true on Monday.
"2013 is the year online went mobile," Anderson said.
Cyber Monday comes after retailers failed to boost spending during the holiday weekend. They offered big discounts in early November, and several opened stores on Thanksgiving Day. But the NRF predicted that spending fell for the first time, down 2.9 percent to $57.4 billion, during the four days that ended Sunday.
About 81 percent of retailers planned to offer deals specifically for Cyber Monday, according to the NRF's online arm, called Shop.org.
The name Cyber Monday was coined in 2005 by Shop.org to encourage people to shop online. After retailers revved up deals for the day, it became the busiest online shopping day in 2010.
But since then, retailers have expanded deals, stretching them into Cyber Week or even Cyber Month. This year, retailers such as Amazon and Wal-Mart rolled out online deals beginning in November.
Belus Capital management analyst Brian Sozzi said that will probably become typical of the start of the holiday shopping season.
"The consumer has become immune to Cyber Monday and Cyber Week," he said. "They just want the discounts continually once the calendar hits November."