How does it work? 

Wireless charging uses electromagnetic induction to send power from the charger to your phone. Wireless chargers have at least one induction coil inside, which creates an alternating electromagnetic field. Phones and other devices with wireless charging have a receiver coil inside that converts the power back into electricity, which in turn, charges the phone's battery.

How fast is it? 

Wireless charging is slower than wired charging, but some wireless chargers and phones support fast wireless charging. If you have an Android phone like the Samsung Galaxy S7 or newer, you can get fast wireless charging. Chargers offer different levels of power in Wattage, which often corresponds to charging speeds. Normal wireless chargers have 5 Watts, so any charger with more Wattage may charge your phone faster, so long as the outlet adapter supports Quick Charge standards.  

What are the downsides? 

Wireless charging is slower, it can heat up your device, some chargers don't work if your phone has a thick case, and wireless charging can't go through metal (hence the glass backs on so many phones). Sometimes it's hard to align your phone properly on the charger or certain chargers decide not to work with certain phones. We emailed every manufacturer in our guide to ask if its chargers support all Qi devices equally — including the new iPhones — and they all said yes, theoretically, so you can count on our picks.

What devices support it? 

Qi is the most popular wireless charging standard, and it seems to have won the war now that the iPhone supports the standard. You can search the Qi database to see if your phone is supported, but most high-end Android phones, the iPhone 8/8 Plus, and the iPhone X support Qi wireless charging. More than 140 devices supported the Qi standard as of 2016, and it's certainly increased since then. Some laptops even charge wirelessly now.