SAN FRANCISCO, United States — Online spending on Black Friday increased 15 percent to a record $1.20 billion as more consumers opted to shop from their couches rather than battling long lines at stores.

Total e-commerce sales reached $20.6 billion in the first 29 days of this holiday season, according to ComScore Inc. That’s about a 3.1 percent increase from Nov. 1 to Black Friday last year, the research firm’s data showed, noting that 2013 numbers include a few more shopping days because Thanksgiving fell on a later date this year.

Consumers are spending more time browsing and buying from smartphones and tablets, on top of the hours they already devote to shopping via the Web on laptop and desktop computers. That’s translating into faster growth in online sales.

“While Black Friday -- and now Thanksgiving Day -- is the traditional kickoff to the brick-and-mortar holiday shopping season, both days continue to grow in importance on the online channel,” ComScore Chairman Gian Fulgoni said in a statement today. “Many consumers prefer to avoid the crowds and lines typically associated with Black Friday by shopping from the comfort of their own homes, and we saw a record 66 million Americans do that this year.”

Thanksgiving Day online purchases climbed 21 percent to $766 million, ComScore reported.

About 97 million people had planned to shop online or in stores on Black Friday, according to the National Retail Federation.

By Danielle Kucera; Editors: Reed Stevenson, Kevin Miller, Pui-Wing Tam