Mobile devices played an important role in shaping a historic Cyber Monday this year, according to data released by Adobe Digital Index, accounting for 28 percent of purchases made during yesterday's event.

Overall, online sales yesterday totaled $2.98 billion, a 12 percent gain from Cyber Monday 2014, according to the ADI. The ADI reported that the average online shopper spent $133 this year.

Besides an increased use of mobile devices to access online sales, tablet use was also up, accounting for about 11 percent of all Cyber Monday sales.

Adobe Digital Index

This year marks the tenth-anniversary of the Cyber Monday event, which was first coined in 2005.

“We can’t emphasize how important the mobile experience is for retailers, especially at this time of the year, when masses of consumers are shopping via their mobile devices,” said ADI analyst Tyler White in a statement.

Overall, online purchases were up the entire holiday weekend, accounting for $11 billion in the days between Thanksgiving and the following Monday. Besides Cyber Monday’s 12 percent gains, Thanksgiving online sales increased 25 percent this year ($1.7 billion), and Black Friday online sales were up 14 percent ($2.7 billion).

Discounts remain the primary reason consumers go online to make purchases during the holiday weekend, according to ADI. Online discounts accounted for 20 percent of Cyber Monday activity this year, and for the other holiday shopping days those gains were even sharper: 26 percent of shoppers cited discounts as their reason for making purchases on Thanksgiving Day, and 24 percent said discounts compelled them to make purchases on Black Friday.

As analysts expected, the uptick in online shopping this year resulted in fewer consumers hitting stores over the holiday weekend. The National Retail Federation this year predicted that more consumers than ever would choose to shop online rather than brave brick-and-mortar stores, which would also result in more consumers making their holiday purchases earlier.