The health code does not record the destination, but the travel card records the destination. Health codes are based on real data. As the electronic certificate where users go in and out, health codes will record the health status of users' places of travel, which are divided into red codes, green codes and yellow codes. The implementation of the health code makes rework and return to work more accurate, scientific and orderly. Users can apply for a health code through Alipay or WeChat, or through a local app.