Shopping through mobile devices soared on Cyber Monday, accounting for more than a quarter of the $3 billion in sales, but many online retailers struggled to get visitors using smartphones and tablets to shop as much as those using desktops.

Bigger-than-expected discounts and strong demand for electronics and toys made Cyber Monday the biggest day for online sales in the United States, according to the Adobe Digital Index report.

The report was based on data from 200 million visits to 4,500 retail websites on what is traditionally the busiest day of the year for Internet shopping.