Online purchases reached USD 1.93 billion on Friday itself, the unofficial start of the retail sector's holiday season.
That marked a 39 per cent increase over 2012, according to software maker Adobe yesterday, which analysed 400 million visits on some 2,000 American shopping websites.
Holiday shopping traditionally accounts for 20 to 40 per cent of an individual retailer's annual sales, according to the National Retail Federation.
Early online Black Friday sales, which began on Thursday, the US Thanksgiving holiday, reached USD 1.06 billion, up 18 per cent from last year, according to Adobe.
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IBM said Internet sales jumped 19.7 per cent over last year on Thanksgiving and 19 percent on Black Friday, with orders averaging USD 135.27, a 2.2 percent increase compared to last year.
Online shoppers may have been wise to avoid stores, with reports of fistfights, a stabbing and a shooting as people elbowed their way through crowded shopping floors to snatch heavily discounted items.
Purchases of smartphones, tablets and other mobile devices accounted for 24.2 percent of online sales, according to Adobe.
IBM also found that mobile devices accounted for 21.8 percent of sales.
According to Adobe, of the USD 3 billion in total online sales over the two days, USD 417 million was done on iPads and USD 126 million was done on iPhones, while Android phones were used to buy USD 106 million in purchases and Android tablets accounted for USD 42 million.
IBM said tablets were used for 14.4 percent of online sales, against 7.2 per cent on smartphones. On average, tablet users each spent USD 132.75 and smartphone users spent USD 115.63.