The Target Web site is shown on a computer screen. (Michael Dwyer/Associated Press)

Online sales were strong on Cyber Monday and throughout the Thanksgiving weekend, an encouraging sign for retailers that invested heavily this year in enhancing their e-commerce offerings.

IBM reports that Cyber Monday sales were up 8.5 percent over last year, while sales for the period from Thanksgiving through Monday were up 12.6 percent.

The uptick came even as retailers had offered both in-store and digital deals earlier in November, creating incentives for shoppers to snap up Christmas gifts long before these traditional promotional events arrived.

The findings make clear just how rapidly consumers’ use of smartphones is changing the shopping experience. Mobile sales on Cyber Monday were 27.6 percent higher than last year, while mobile devices for the first time accounted for more than half of online traffic on Thanksgiving.

But the data also reveals that smartphones still primarily remain a tool for browsing, not buying. Smartphones accounted for 28.5 percent of total online traffic on Cyber Monday, and yet represented only 9.1 percent of total online sales.

Tablets, it seems, are used differently. They accounted for 12.5 percent of all online traffic, and yet they represented 12.9 percent of online sales. So tablet shoppers are closing the deal much more frequently than smartphone shoppers.

And although a desktop PC may not be the trendiest way to browse the Web, these devices still accounted for the lion’s share of online shopping on Monday. Desktop PCs account for the majority of online traffic and 78 percent of online sales. Consumers’ average order value was also highest on desktop.

IBM analyzed the differences between shoppers who used Apple’s iOS operating system and those who used Google’s Android. The company found that iOS users averaged $114.79 per order, compared with $96.84 for Android users. Users of Apple’s iOS also accounted for a larger share of online traffic and sales on Cyber Monday than Android users.

Adobe issued a separate analysis of Cyber Monday shopping that found that overall sales hit $2.65 billion, a 16 percent increase over last year. The technology company says that large retailers had the healthiest bumps in sales: The top 25 retailers in the United States saw 25 percent year-over-year online sales growth on Monday, while smaller retailers had growth of only 5 percent.

As has been the case in previous years, shopping peaked between 9 and 10 p.m., according to Adobe’s analysis of 400 million visits to 4,500 retail Web sites.

Wal-Mart, the nation’s largest retailer, said that it recorded its biggest day of orders ever on Cyber Monday, though the company did not disclose how many orders its received.  Its Web site, Walmart.com, drew 1.5 billion pageviews between Thanksgiving and Cyber Monday, a five-day period in which the retailer was continuously offering fresh rounds of deals and promotions.

In a sign of how the lines between digital and in-person shopping are blurring, Wal-Mart reported that it saw a 70 percent increase on Cyber Monday in online orders that were picked up in stores.