Free shipping remains the king of online shopping perks, according to the fourth annual survey of digital buying behavior conducted by research firm comScore Inc. and transport and logistics giant UPS Inc.

Of more than 5,000 online shoppers surveyed, 77 percent said that free shipping remains the most important option during the checkout process. About 60 percent of respondents said they add items to their online cart to qualify for free shipping. More than 80 percent said they are more likely shop with an e-tailer that offers free shipping.

Bala Ganesh, UPS' retail director, said consumers naturally gravitate to an offer of free shipping even if they know the shipping cost may already be embedded in the supply chain process and be reflected in the selling price. "They understand that free shipping may not necessarily be 'free,' per se, but whether or not they internalize it is a different question," Ganesh said in an e-mail.

Ganesh said consumers give little thought to the implications of a free shipping offer, and essentially expect it. He also disputed the notion that there is a trade-off in the form of higher selling prices. "Retailers today are in a position where they have to offer free shipping in order to keep up with the competition and (to) satisfy consumers," he said. "They don't necessarily have the power or the luxury to increase their selling price just to make up for the cost they may incur if they provide free shipping."

The survey also found that nearly half of respondents have requested that goods they ordered online be shipped to a store for pickup. About 45 percent made an additional purchase at the store when picking up their online orders, the survey found.

According to the report, 62 percent said they were satisfied with the online returns process; 67 percent review a retailer's return policy before buying; 66 percent want free return shipping, and 58 percent want a "no questions asked" returns policy. When an online purchase is made from a retailer that also has a physical presence, 61 percent return the item to the store in person; when doing so, 70 percent will purchase an additional item, according to the survey.

More consumers are open to alternate delivery options than they were last year, the survey found. This year, one-third said they preferred to have packages delivered to locations other than their home. Last year, the figure was 26 percent.