Traditional retailers are facing the same problem, of course, and discounts are proliferating from suburban malls to Fifth Avenue. But the price-cutting is fiercest on the Web, where customers can easily shop for the best price with a quick search on Google or on specialized shopping engines like Shopping.com. Online, the competition is only a click away. For many Web sites, the discounts and price cuts are the only way to hold on to customers as online buying unexpectedly plummets. The research firm comScore reported Tuesday that sales growth on e-commerce sites slowed to a meager 1 percent in October compared with the previous year  the lowest rate ever for online retail and well down from the industry’s typical 20 percent gains.

Sales of music, movies, books, computer software, flowers and gifts have been hit the hardest, with double-digit declines, comScore said. “A lot of these retailers aren’t running on big margins to begin with, so it’s pretty challenging,” said Gian Fulgoni, chairman of comScore. “But it’s a Catch-22 situation: They have to run these deals because that’s what consumers are looking for this season.”

To preserve the sanctity of their brands and some level of pricing control, some Web companies are promoting discount sites separately from their main brands. Zappos.com, a shoe retailer based in Henderson, Nev., never runs promotions on its site. Instead, it quietly moves shoes that do not sell in six months to 6pm.com, a clearance site it acquired last year, but runs separately. This month, the company is buying more search ads for 6pm.com, where a pair of colorful slip-on Keds sneakers is on sale for $12.73  74 percent off the original price on Zappos.com.

Even when these extreme discounts mean selling shoes for less than Zappos.com paid for them, it is better to recoup some cash than none, said Tony Hsieh, the company’s chief executive.

The discounting is not just drastic, but is also occurring unusually early in the season. Kmart, a division of Sears Holding, initiated Black Friday prices on electronics  40 to 50 percent off  on Nov. 2, nearly four weeks before the real Black Friday, the busy shopping day just after Thanksgiving that usually marks the beginning of the holiday buying season.