Online sales rose faster than expected in the US on Black Friday, according to surveys.
Internet sales totalled $816m (£524m), a 26% gain on last year, said Comscore. IBM Coremetrics put the rise at 24%.
Black Friday, the day after Thanksgiving, is treated by many retailers as the start of the Christmas shopping season. They offer one-off discounts to mark the occasion.
Analysts said heavy promotional activity helped drive demand.
By comparison, a report by Shoppertrak suggested that in-store Black Friday sales were up by 7% on last year, at $11.4bn.
Beating the rush
Around 50 million Americans visited online retail sites on Friday, according to Comscore.
It said Amazon was the most popular destination, with 50% more visitors than any other retailer.
Walmart, Best Buy, Target and Apple were next in line, said the analytics company.
"Despite some analysts' predictions that the flurry of brick-and-mortar retailers opening their doors early for Black Friday would pull dollars from online retail, we still saw a banner day for e-commerce," said Comscore's chairman, Gian Fulgoni.
IBM Coremetrics also noted a trend towards shopping on smartphones and tablet computers.
It said Black Friday purchases made on mobile devices had accounted for 9.8% of all online sales, compared with 3.2% last year.
IBM described mobile shoppers as having had a "laser focus" since they had been more likely to view a single page on a retailer's site rather than browse what else was for sale.
IBM said Apple's iPhone and iPad had generated the most mobile internet visits to online stores, accounting for more than double the traffic originating from devices running Google's Android system.
The company also noted a jump in Black Friday related chatter on social networks. It recorded a 110% rise in discussion volumes after consumers had shared tips on how to secure products before they sold out and the best places to park.
Friday's internet sales are expected to be eclipsed today on what is referred to as Cyber Monday - which many experts believe will be the US's busiest online shopping day of the year.
Close to 123 million Americans plan to make an online purchase according to a survey commissioned by the US National Retail Federation, an industry lobby group. That would be a 15% increase on last year.
NRF said nearly eight in ten online retailers would run special promotions including "flash sales that last an hour" and "free shipping offers".
The federation also highlighted the shift to mobile devices, saying it expected 17.8 million Americans to use them to shop today, nearly five times the number in 2009.
"Retailers have invested heavily in mobile apps and related content as the appetite for Cyber Monday shopping through smartphones and tablets continues to rise," said Vicki Cantrell, executive director of the NRF's website shop.org.
UK internet retailers said it was less clear which day will be the UK's busiest online shopping day this year.
"Over the last couple of years we have seen a fortnight of peak activity over the period corresponding to both this and next week," said Andy Mulcahy, a spokesman for the industry body Interactive Media in Retail Group (IMRG).
"We expect £3.72bn will be spent online over the two week period."
Mr Mulcahy said that although some retailers are trying to generate interest in the idea of a cyber event in the UK, but they are split over which day to mark.
Visa Europe said it believed today will be the UK's busiest internet shopping day, with £303m spent online.
eBay has forecast that it would experience its peak in activity this Sunday with more than 5.5 million people expected to log onto the UK version of its auction website.
Amazon said it expected to experience more demand the following day.
"In recent years, the first Monday in December has been Amazon.co.uk's busiest day with orders for over 2.3 million items being placed on Monday 6th December last year," said Christopher North, the website's managing director.