Peak spending to take place on Monday, with 125 million visits.
British shoppers are poised to spend £1.5bn online over the Black Friday/Cyber Monday weekend, according to Sage Pay.
Spending will likely peak during Monday at £600m, with website visits hitting 125 million and noon set to be the busiest period of the day for the third year running.
Simon Black, chief executive at Sage Pay, said: "With just four weeks until Christmas, Cyber Monday is traditionally the day when consumers rush online to do their festive shopping."
Online shopping on the Black Friday weekend has been on the increase for the past few years, with the UK spending £500m on Cyber Monday alone last year for the first time, a 15% increase on the previous year.
Since 2009 spending on Cyber Monday has increased by more than £250m, with the volume of transactions rising by an average of 11.25% over the last four years.
"This expenditure growth is a direct result of increased UK consumer confidence in spending," Black added. "As the UK’s economy begins a period of upturn after suffering during the 2008 recession, we believe that this confidence will continue into the Christmas period."