That depends. Usually if your luggage is ticketed through to your final destination, you don't have to. However, if you're traveling internationally, you may be required to pick up your luggage and have it screened again at your first entry into the country.

On a domestic United Airlines flight within the U.S., your checked bags are typically checked through to your final destination, meaning you do not need to pick them up during a layover. However, there are two major exceptions. First, if you are arriving on an international flight and connecting to a domestic one (e.g., London to Houston to Denver), you must collect your bags after clearing immigration, walk them through customs, and drop them at the "baggage re-check" counter. Second, if your layover is an overnight connection or longer than 12 hours, United may require you to claim your luggage and re-check it the next morning. Always check the destination code on your baggage tag at the initial check-in; if it lists your final city, the airline usually handles the transfer for standard domestic connections.