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Between Cyber Monday’s record-breaking sales, and the myriad of fashion tech startup companies that seem to crop up every week, there’s no doubt that the way Americans shop has been completely revolutionized the past few years–a fact made increasingly clear this holiday season.

Some of the biggest retail trends to come out of the Christmas season were an increase in online and mobile shopping, reduced foot traffic at brick-and-mortar stores, and consumers’ focus on deals, leading to sales spikes on Black Friday and late December, according to WWD.

If you left all your Christmas shopping to the last minute, well, you’re in good company. December 22, the Saturday before Christmas, was one of the biggest shopping days of the season–a larger volume day than even Black Friday, according to RetailNext’s chief marketing officer Tim Callan. Callan also said that Dec. 19 to 21 were among the top-five buying and traffic days of the season.

But while shoppers hit the stores in droves as the Christmas holidays loomed ever closer, most retailers saw unusually lackluster sales in early to mid December, causing many to worry about meeting their projected numbers this quarter.

One of the reasons sales and store traffic were down–besides shoppers’ procrastination, and an overall gloomy mood thanks to the approaching ‘fiscal cliff’–is because consumers are more strategic about how they spend their time and money.

“Most consumers have done some sort of research before they go into the store, and they have a better idea of what they want,” Shelley Kohan, RetailNext’s vice president for retail consulting, told the trade. “That’s part of the double-digit traffic decline — a lot of people, when they get to the mall, are visiting two or three stores instead of four or five.”

And, of course, another reason foot traffic was down at brick-and-mortar stores is because online sales were up–way up. The second week of December, from the 10th to the 16th, broke records to become the first $7 billion week in online history.

Typically, online sales begin to dwindle in mid to late December as last-minute shoppers tend to favor brick-and-mortar buys to costly expedited shipping fees. But not this year. Thanks to Free Shipping Day on December 17th, and innovative methods from retailers like eBay’s Holiday Express, which provides product delivery in as little as one hour after a mobile purchase is made, online sales were up 52.8 percent from the corresponding period last year. Free Shipping Day raked in a whopping $1 billion alone, while the five day work week period from December 17th to December 21st hit $3.69 billion.

Mobile sales were also through the roof. Sunday December 9, which is apparently “Mobile Sunday,” was the heaviest mobile shopping day, with both eBay and PayPal hitting record daily highs in mobile volume–higher even than Cyber Monday.

There’s no doubt that it’s a brave new world when it comes to how consumers shopped this holiday season–the one question that remains, though, is how retailers will adapt.