U.S. desktop ecommerce holiday spending was already up 14% year-over-year by for the first 24 days, ahead of Black Friday.

Black Friday itself, comScore reports, was the first billion dollar online shopping day of the holiday season with $1.198 billion in desktop ecommerce in the U.S. According to the firm, as of December 1st, holiday online shopping in the country has reached $20.6 billion so far, up 3% from last year.

If that doesn’t seem like much growth, it’s because of a variation in the 2012 and 2013 shopping calendars with Thanksgiving falling later than usual this year. Last year’s numbers contain a full week of heavy post-Thanksgiving/Cyber Week buying, comScore says, so the growth rate is being “artificially suppressed in the short term.” The effects, it says, will normalize as the holiday season goes on.

Black Friday was the heaviest online spending day to date, up 15% compared to Black Friday last year. Thanksgiving saw 21% growth year-over-year, reaching $766 million.

“While Black Friday – and now Thanksgiving Day – is the traditional kick-off to the brick-and-mortar holiday shopping season, both days continue to grow in importance on the online channel,” said comScore chairman Gian Fulgoni. “Clearly many consumers prefer to avoid the crowds and lines typically associated with Black Friday by shopping from the comfort of their own homes, and we saw a record 66 million Americans do that this year. Also interesting is that the recent trend of kick-starting holiday shopping by opening stores on Thanksgiving Day seems to be having a spillover effect on the online channel. Thanksgiving once again posted a well above average growth rate and is the fastest-growing online shopping day over the past five years, as more Americans opt for couch commerce following their Thanksgiving Day festivities.”

Believe it or not, Amazon had a major impact on Black Friday shopping. 66.1 million Americans visited online retail sites on Black Friday from the desktop (up 16% from last year, and Amazon was the top site, followed by eBay, Walmart, Best Buy and Target.

27% of sales went to apparel and accessories with 19% going to computer hardware, 7% to consumer electronics, 5% to consumer packaged goods, 5% to shipping services and 36% to everything else.

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