The approach worked: The company racked up US$1m in revenue in its first four weeks. In 2015, its first full year, sales topped US$100m. Casper mattresses are now also sold at Target stores.
The company's success has given way to a number of other online mattress start-ups, including Leesa, Tuft & Needle, Helix Sleep and Pangeabed.
Even Walmart is jumping in: Allswell, a premium mattress and bedding brand targeted to affluent online shoppers, is scheduled to launch next week.
The basic premise of the companies is the same: Buy a mattress online and try it for 100 nights. If you don't like it, they'll give you a full refund. (In most cases, returned mattresses are donated to charity.)
But back in 2014, it wasn't necessarily an easy sell. Shoppers weren't accustomed to spending hundreds on a mattress they'd never seen or touched.
Krim said he knew it'd be a challenge to get people to buy mattresses sight-unseen, but what he didn't expect was a steady stream of shoppers who stopped by Casper's office, a one-bedroom New York City apartment, to test out the company's wares.
"On day 1, we had someone knock on our door and say, 'I'm here to try out the mattress,'" Krim said. "That's when we realized, by accident, just how important the physical experience was going to be."
Employees quickly turned a conference room into a makeshift bedroom and invited potential customers to stop by.
"We said, 'Take however long you need. Fall asleep, take a nap,'" Krim said. "It felt like a bedroom. It was the antithesis of the traditional big mattress experience with fluorescent lights and a pushy salesman."
Over the years, Casper has hosted 16 pop-ups across the country. The company also has "Napmobiles" - trucks fitted with four napping pods - that cruise the country, offering customers a chance to snooze on one of its mattresses. (Having trouble dozing off? The pods come equipped with privacy blinds and pre-recorded bedtime stories.)
Now Krim says the company is making that experience permanent, with its newest store at 627 Broadway. The location will have six mini-bedrooms where customers can stop by to test a range of products, including pillows, sheets and duvets. (And as for, um, inappropriate behavior under the sheets, a Casper spokeswoman says, "We're not worried. We've been testing the concept in other locations.")
The company is the latest internet retailer to expand offline. A number of others, including eyeglass maker Warby Parker, shoe company M. Gemi and socially-minded clothier Everlane, have also opened physical locations in recent years. It's an approach that makes sense, Krim says, as customers seek new experiences. The store will also host community events focused on sleep and wellness.
"Buying a mattress or sheets or pillows is one of the most intimate purchases you'll make," Krim said. "You should be mentally relaxed and comfortable so you can find the right product."