Yes, you can use a valid U.S. passport as your primary identification to enroll in and use CLEAR. When you first sign up for the service at an airport kiosk or via the mobile app, you must present a government-issued photo ID; a U.S. passport is one of the most widely accepted forms, along with a driver's license or a permanent resident card. Once your identity is verified and your biometrics (iris and fingerprints) are scanned, your "CLEAR Plus" profile is linked to your passport data. In 2026, the CLEAR app also features a "Vault" where you can upload a digital copy of your passport to serve as a "REAL ID" equivalent. When you arrive at the security checkpoint, you simply scan your eyes or fingers at the CLEAR pod, and a CLEAR ambassador escorts you to the front of the line, bypassing the standard document check where you would normally show your physical ID to a TSA officer. However, you should always carry your physical passport or ID with you, as the TSA reserves the right to perform a manual random check, and you will certainly need the physical document once you reach the boarding gate or arrive in a foreign country.