A carry-on bag is a small piece of luggage that travelers can bring onto an airplane. It is designed to fit in the overhead compartment or under the seat in front of you. Most airlines have specific size limits for carry-on bags, typically around 22 x 14 x 9 inches, but these can vary. Carry-on bags are convenient for keeping essential items close during a flight, such as clothing, toiletries, and electronics. They help travelers avoid checked baggage fees and reduce waiting time at the airport. Many people choose to use backpacks or rolling suitcases as their carry-on options.