After applying for the health code, you can know where you have been by using the positioning system and big data analysis. For sensitive information such as ID number and mobile phone number, the page display will hide sensitive information when presenting health code; The right of collectors to view and modify information will be strictly controlled. Online health code is one of the ways to collect citizens' health information, and the specific travel policy is mainly based on the policies issued by various regions and the guiding documents issued by the government.