(CNN) -- After years of being more hype than highlight, Cyber Monday appears on its way to its biggest outing ever.
Last year, the Monday after Thanksgiving saw an estimated $1 billion spent online in the United States, making it the biggest e-sales day ever. And analysts said Monday that this year's "holiday" -- the online answer to the annual Black Friday bargain rush on stores -- is on pace to be bigger still.
As of 3 p.m. ET, online sales were up 15% from last year, according to IBM Benchmark (formerly Coremetrics).
The analytics group, which monitors sales on more than 500 online retail sites, has been reporting Cyber Monday sales for the past four years.
As a marketing term, "Cyber Monday" was coined in 2005. But, according to IBM and others, it wasn't until 2009 when the Internet saw more sales that day than on Black Friday. And last November was the first in which Black Friday actually ended up being the biggest online shopping day of the year.
"We at comScore have spent a lot of time in past holiday seasons dispelling the notion that Cyber Monday was the heaviest online spending day of the year," said Andrew Lipsman of the Web analytics firm on its blog. "And just when it seemed that message finally began to sink in, Cyber Monday has a banner year and jumps to the top of the ranking. "
A growing push by retailers has helped morph perception into reality, said IBM's John Squire.
"Now that we're starting to see some retailers promote Cyber Monday in their stores, I think we're really starting to ingrain this as the 'next big shopping day,' " said Squire, chief strategy officer for IBM Smarter Commerce.
From Amazon to Best Buy to Macy's to Walmart, virtually every major online retailer was touting Cyber Monday deals. Even nontraditional businesses such as airlines and hotels were getting in on the act with Monday travel discounts.
About half of all online shopping on Cyber Monday happens on consumers' work computers, according to comScore.
Another significant trend is how many people are now shopping with their phones or other mobile devices.
More than 12% of the people surfing retailer sites were using mobile devices, according to IBM Benchmark, and more than 7% of the purchases made were on mobile. That's up from 3.2% last year.
"When you look at the numbers ... you can really see how fast the mobile experience and the mobile user is impacting online sales," Squire said.
Retailers were making their marketing push with gusto on Monday, with promotions for online sales popping up almost every time you clicked.
On Twitter, the hashtag #CyberMonday appeared to be used more often by vendors promoting deals than by shoppers talking about their experiences. In fact, a wireless company paid to make #CyberMonday a "sponsored tweet," guaranteeing that its own deals appeared prominently when someone searched for that term.
Rank-and-file Twitter users were taking notice of the sales blitz.
"I live every Monday like it's #CyberMonday," wrote Twitter user Ryan Chapman. "I.e., under a constant barrage of email, tweets, & Facebook posts."