the Advance Input System (Q-CODE) user manual
From '22. 4. 1.(Fri), Korean time, not only those who have completed domestic vaccinations, but also those who have completed overseas vaccinations who have not registered their overseas vaccination history with the Korean public health center will be exempted from quarantine if they use the Q-code to enter quarantine information in advance.
those who plan to enter Korea through Incheon, Gimhae, or Daegu International Airports are encouraged to use the convenient Q-code for quarantine information