Communication Big Data Travel Card is a free inquiry service provided by China ICT Institute, China Telecom, China Mobile and China Unicom for mobile phone users in China. Mobile phone users can query all the city information they have visited in the previous 14 days through this service.
Health codes are based on real data and can be generated by citizens or people who have returned to work through online declaration and background audit. As an individual entering and leaving electronic certificate locally, the QR code can be declared once, which is universal in the whole city.