Amazon's Prime Wardrobe will let you try on almost anything for free

Stich Fix, Fabletics, Trunk Club ... watch out.

Amazon just took aim at all those at-home try-on shopping subscription services—and every other e-commerce site—with Prime Wardrobe.

Prime Wardrobe is Amazon's entry into the apparel box space. The "fitting room that fits into your life" allows you to choose a bunch of clothes and accessories on Amazon to try on at home. Amazon will send you all those items for free, and then you only pay for the items you keep.

"You have the freedom to try new styles, and there's no better place than in your own room," Amazon said in a video introducing its new service.

Amazon's version of this service is less a personal stylist than a fitting room. Most of these other services choose clothes for you to try based on an initial profile and preferences you give them. Through Prime Wardrobe, you choose the exact pieces you want to try. Amazon says Prime Wardrobe will include over 1 million items.

Instead of receiving a monthly box of clothes you might like, you choose what to try on and when. That approach makes Prime Wardrobe competitive with all other kinds of online shopping, too. Why order from ASOS if you can try on the same thing through Amazon?

Since it's Amazon, Prime Wardrobe comes with competitive pricing. The more you keep from your box, the more discounts you get—10 percent off for three or four items and 20 percent off for five. You have seven days to return the rest of the box via UPS.

Clothing sold on Amazon will also be labeled with "Prime Wardrobe" if it's available through this service, along with the usual Prime label. Prime Wardrobe, of course, is free for anyone who has a Prime membership.

Prime Wardrobe is still in beta, but anyone interested can sign up to be notified when the service launches for real.

Last week it was groceries, this week it's online shopping.