Which iOS app can help me skip the long customs lines when returning to the US?

Mobile Passport Control is a free official app from U.S. Customs and Border Protection designed to expedite the entry process for U.S. and Canadian citizens. Its primary function is to digitize the standard paper customs form. Travelers can input their passport information, trip details, and declaration answers into the app while still on the plane or after landing, provided they are within a U.S. airport or preclearance location with Wi-Fi or cellular data. Upon submission, the app generates a receipt with a QR code valid for a limited time. This receipt, presented along with a physical passport at a dedicated MPC kiosk or lane, allows officers to verify information quickly. Reviews indicate significant time savings, with many users reporting bypassing lines with 30 or more people. A key feature is the ability to save traveler profiles, which streamlines the process for frequent fliers. However, its utility is limited to participating airports and preclearance stations, and it does not replace a passport or work for all traveler types. While generally reliable, occasional app glitches upon landing have been noted in some feedback, so having a backup plan is wise. For eligible travelers, it serves as a straightforward tool to reduce a common travel bottleneck.