Any drone over 0.55 pounds (and up to 55 pounds, including the camera) must be registered with the FAA. Tiny drones — those that fit in the palm of your hand, more or less — don’t need to be registered. Anything larger than 55 pounds must go through a separate registration process.
You must also be 13 years of age or older, and a US citizen.
The registration will cost $5, but it’s refundable until January 20. The FAA says drones need to be registered before flying them outdoors.