The Federal Aviation Administration says unmanned aircraft systems, or drones, are aircraft, and not toys. That means you need to register any drone that weighs more than half a pound.
The FAA says all drones that weigh more than 0.55 pounds have to be registered, whether you're using it for a hobby or commercially. If someone from law enforcement asks you about operating your drone, you'll need to show them the registration paperwork.
Drone operators must also keep the drone in sight while flying, even if the drone has a camera. You're also not allowed to fly a drone within about five miles of an airport or military base.