Health codes are not handled by themselves, but by family members. Local health codes need to be handled by relatives and friends, and one person can bind many people to support family and friends to collect health codes on their smartphones.
Health code is a personal two-dimensional code based on actual real data, which is declared by citizens or people who return to work after self-declaration. After background review, the QR code is generated as a electronic certificate where individuals enter and exit locally, which realizes one-time declaration and is universal in the whole city.