Black Friday online sales rose to $1.04 billion from $816 million on 2011's Black Friday, research company ComScore said.
U.S. shoppers would likely spend a record $1.5 billion on Cyber Monday, $250 million more than in 2011, the company said.
The most-visited retail site Friday was Web-only retailer Amazon.com, followed by the websites of brick-and-mortar stores Walmart, Best Buy and Target, and then by Apple, ComScore said.
Online spending throughout the holiday season is expected to increase 17 percent to $43.4 billion, ComScore said.
Cyber Monday, created by the online branch of the National Retail Federation in 2005, is a marketing term for the Monday after Black Friday, which itself is the day after the U.S. Thanksgiving.
The term is now used by online retailers in Canada, Britain, Portugal, Germany and Chile.