This is the biggest hint yet that Apple's next iPhone will have wireless charging

Apple has joined the Wireless Power Consortium, an industry group that develops a widely-used wireless charging standard that can be found on devices like Samsung's Galaxy S7 smartphone.

Apple joined WPC late last week, a WPC spokesperson confirmed to Business Insider. WPC oversees a charging standard called Qi that insures interoperability among different products and brands that support wireless charging.

When using a Qi charger, the user merely drops his device on a compatible charging pad and it can draw power without plugging a cord in, although the pad needs to be connected to the wall.

Although Apple's iPhone 7 doesn't use wireless charging, unlike many of its smartphone competitors, the Apple Watch uses a proprietary wireless charging puck to charge up. However, that puck is not compatible with other Qi chargers.

The Apple Watch charger is using a modified version of Qi that is not interoperable with other wireless chargers, a former WPC executive told Business Insider. "The Apple Watch charger that comes with the device is Qi based, but the firm decided not to submit it for interoperability testing," a former WPC VP said in 2015.

Despite Apple's penchant for secrecy, it frequently joins important industry groups so it can participate in the development of new technologies and understand where they're going. For example, it recently hosted a meeting of the Unicode Consortium at its headquarters.

Apple is rumored to be adding wireless charging to the next model of the iPhone, which is expected to launch this fall.