U.S. online sales grew 14 percent on Cyber Monday, on track to set a record, leading some retail websites, like Target Corp's, to crash temporarily due to high customer traffic.
Website outages and slow checkouts during the five-day shopping spree starting Thanksgiving Thursday, were also reported at PayPal Inc, department store chain Neiman Marcus, Wal-Mart Stores Inc, L Brands Inc's Victoria Secret, and at Foot Locker Inc.
Sales on Cyber Monday, the busiest day of the year for internet shopping, were up 14 percent from a year earlier at $490 million between midnight to 10 a.m. ET, according to Adobe Digital Index, part of Adobe Systems Inc, which provides digital marketing and media solutions to merchants.
Adobe tracked 80 percent of all online transactions from the top 100 U.S. retailers and said sales are on track to meet its expectation of a record $3 billion by the end of the day.
The data underscored the ongoing shift in shopping to online retailers.
To compete with each other and Amazon.com Inc, most U.S. retailers like Wal-Mart, Target, Best Buy began offering some of the season's best online deals, which traditionally had been reserved for Cyber Monday, several weeks in advance.
This hurt spending and customer traffic at stores during Thanksgiving evening and Black Friday.
"Consumers are hyped for Cyber Monday, with social buzz more positive than what we saw on Black Friday, but they need to brace themselves for the highest out-of-stock rates of the season so far," said Tamara Gaffney, principal analyst at Adobe Digital Index.
Adobe said 15 out of 100 product views were returning an out-of-stock message this morning, two-and-a-half times the normal rate.
Between Thanksgiving Day and Sunday, $8.03 billion was spent online, a 17 percent increase from 2014, Adobe said. The average shopper spent $135.25, up 4 percent from a year ago.
Mobile, which includes phones and tablets, accounted for 53 percent of shopping visits driving 32 percent of online sales, the data showed.
IBM has predicted Cyber Monday online sales will grow by more than 18 percent compared to 2014.
(Reporting by Nandita Bose in Chicago; Editing by Nick Zieminski)