Clothing companies for years have struggled to curb costly online returns, as customers send back piles of ill-fitting jeans, too-tight dresses and shoes that don’t look quite as expected.

Now is encouraging customers to try clothing — and return it — with abandon.

The company’s newest feature, called Prime Wardrobe, allows Prime members to pick from more than 1 million pieces of apparel that they could order, try on and return free. Shoppers would pay for only what they keep and would receive discounts based on the number of items they hold onto. (For instance, customers would receive 10 percent off for keeping three or four items from their order, and 20 percent off for keeping five or more pieces of clothing.)

The selection of clothing, shoes, handbags and other accessories would include Amazon’s private labels, as well as brands such as Calvin Klein, Theory, Hugo Boss, Lacoste and Carter’s.

“Prime Wardrobe brings the fitting room to you,” Amazon said on its website Tuesday. Prime Wardrobe is currently in beta testing, but customers can sign up online to be notified when the service formally rolls out in their region. (Jeffrey P. Bezos, Amazon’s founder and chief executive, owns The Washington Post.)

The items would come in a resealable box, with a prepaid return shipping label. Customers could then drop off their returns at a UPS store or schedule a free pickup.

Amazon’s foray into fashion could deal another round of bad news to an industry already dealing with turmoil. Clothing retailers such as Macy’s, Sears, Abercrombie & Fitch, and BCBG have been struggling with months of declining sales as customers increasingly shop online. Prime Wardrobe would also compete with subscription-style services such as Stitch Fix and Nordstrom’s Trunk Club, which send customized selections based on a shopper’s sizes and preferences.

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