Cyber Monday: Who Won Online Shopping's Biggest Day?

Monday is set to break shopping records, becoming America's largest-ever online shopping day. Some $6.6 billion in sales will be generated, according to Adobe Analytics, which tracks 80 percent of online shopping activity. By 10 a.m. Monday, $840 million had already been spent online, Adobe said  a jump of 17 percent from the year before.

It's notable that spending on Cyber Monday typically peaks in the evening, between 8 and 11 p.m., so reaching $800 million well before noon indicates a strong start to the day. 

So where are we spending all that money? In a word: Amazon (AMZN). The e-commerce giant accounts for somewhere between 45 percent and 50 percent of all sales by volume, according to separate estimates from SunTrust Robinson Humphrey and GBH Insights.

Amazon's revenue take is somewhat smaller, thanks to the large number of third-party sellers on its platform. Amazon will have about 24 percent of the online shopping share this holiday season, STRH estimated, up from 20 percent last year. 

eBay (EBAY), the online auction site, is the second-largest online shopping site, but its share of sales is in the "high single digits," said Youssef Squali, managing director and senior analyst at STRH. Walmart (WMT) is No. 3.

Other factors feed into making this an exceptionally strong season for Amazon, not least of which is the availability of the Echo speaker and other "smart home" devices, which funnel shopping through the giant cybermerchant.

"Given a record breaking Prime Day in 2Q, continued momentum in 3Q, and the fact that this is just the second holiday season offering monthly Prime memberships (a service we view as most compelling during the holidays), we expect a record breaking holiday season for the company," STRH analysts wrote in a note. Amazon's market share typically peaks in the fourth quarter, they added.

The breakneck pace of Cyber Monday shopping comes on the heels of a strong retail showing over Thanksgiving day and Black Friday, the latter of which set an online sales record. Macy's (M), JCPenney (JCP) and Kohl's (KSS) each reported strong or record-setting sales over the weekend. Foot traffic in stores on Black Friday fell only about 1 percent from last year, according to Shopper Trak -- less than many had feared.

Shoppers are bolstered by record stock market highs and soaring home values, analysts said.

"The economy is doing well, and when consumers feel confident, they're going to spend," said Aaron Shapiro, CEO of Huge, a digital marketing company.

"So far it's been a really strong holiday season. The biggest winner has been the internet," said Shapiro. "Combined with the fact that people tend to shop at the last minute , that portends a really strong holiday shopping season."

Big as it may get, Cyber Monday is no match for the world's largest shopping holiday. That would be China's Singles' Day, on Nov. 11, which this year generated a whopping $25 billion in sales (not to mention some 300,000 tons of carbon dioxide). Not bad for a holiday that's less than a decade old.