Workers pack a lorry on Monday at Amazon.com's huge plant in Phoenix, Arizona The US is projected to have had its biggest ever online shopping day, according to analysts.Research firm Comscore said consumers would have spent $1.5bn (£0.9bn) on so-called Cyber Monday, up 20% from last year.
Online-sales tracker IBM Benchmark put the internet shopping rise even higher - up nearly 27% compared with the Monday after Thanksgiving last year.
Smartphone and tablet computer sales rose 10.2%, said IBM Benchmark.
"Online's piece of the holiday pie is growing every day, and all the key dates are growing with it," Forrester Research analyst Sucharita Mulpuru told Associated Press news agency.
"The web is becoming a more significant part of the traditional brick-and-mortar holiday shopping season."
Online sales also jumped sharply on so-called Black Friday, which is the day after Thanksgiving.
Comscore said internet shopping rose by a quarter last Friday to break the $1bn mark for the first time, while it was up by a third on Thanksgiving itself.
There was also a jump in consumer spending this Thanksgiving weekend compared with last year, retailers say.
A record 247 million people visited stores and websites between Thursday and Sunday, spending a total of $59.1bn, 13% more than last year, the National Retail Federation (NRF) said.
The average shopper spent $423 over the weekend, up from $398 last year.
Despite the jump in sales over the weekend, there are concerns that the rise in spending over the festive period as a whole will be weaker this year.
The NRF has forecast a 4.1% increase in retail sales during November and December, less than the 5.6% jump recorded last year.
