Mobile technology is key to Hilton Worldwide’s future.

In July, Hilton tested a new type of hotel door key in which guests with the HHonords app on their smartphones can unlock their hotel doors by pressing a button in the app.

Hilton installed Bluetooth-enabled locks into its doors to make that work. When the guest is within five feet of the door, an unlock button will appear in the guest’s app, says Dana Shefsky, director of digital product innovation at Hilton Worldwide. The guests presses it to unlock the door. The key unlocks a guest’s hotel room, the elevators, side doors, the fitness center and the parking garage.

Across the 18 properties testing the system since July, more than 6,000 Hilton guests have requested to use a Digital Key during their stay.

“We are expecting those usage numbers to grow exponentially by the end of the year as we add more hotels and ramp up marketing,” Shefsky says.

To use the technology, a guest must be a member of HHonors, Hiltons’ rewards program, and must use the mobile app’s Hilton’s digital check-in feature. Digital check-in allows Hilton guests to check in to their rooms via a smartphone, tablet or computer. They can select their preferred room from a digital floorplan any time after 6 a.m. of the day of their stay. Guests also need to have Bluetooth turned on in the settings of their smartphone and have an iPhone 4s or later running iOS8 or later, or Android 4.3 or later.

Instead of installing a new door for each hotel room, Hilton is retrofitting the Bluetooth technology into each door. This costs significantly less than getting a whole new door, Shefsky says although she declines to reveal the cost of the program.

Digital Key is scheduled to be available by Q1 2016 at 250 Hilton properties in the Hilton Hotels & Resorts, Waldorf Astoria Hotels & Resorts, Conrad Hotels & Resorts and Canopy by Hilton brands, unlocking 170,000 doors, Shefsky says.

Having the Digital Key eliminates guests from waiting in line to check in and receive their keys.

“We’ve also had guests find a line at the front desk upon arrival, only to pull out their app, check in, and immediately get a Digital Key,” Shefsky says.

When a guest checks in in the app, the app asks if he wants to use a Digital Key. More than 80% of guests who have used digital check-in have chosen to use the Digital Key. Guests who digitally check in but don’t choose a Digital Key must wait in an express line to pick up the physical key. With the Digital Key, guests can just walk directly to their rooms.

“After a long day of travel, many of our guests just want to get to their rooms,” Shefsky says. “We’re helping them get there quicker, leveraging technology to put them in control.”

If a guest selects use a Digital Key, the key will be issued to the guest as soon as the room is ready. The guest will receive an alert on his smartphone that the Digital Key is available. Currently, only one guest per room can have access to the key button on his smartphone because it is unique to the room reservation in the app. If guests need multiple keys, a physical key will also work for the door. Hilton removes the key button from the app when the guest checks out.

Since last summer, the HHonors app has been downloaded two million times. Seven million guests have used digital check-in since the service rolled out in July 2014, Shefsky says. 93% of guests who have used digital check-in are satisfied or extremely satisfied with the experience, Shefsky says.

Other features in the app for HHonors members including booking a room, room service requests and exploring nearby restaurants and bars.

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