Permission granted by port health authorities for a vessel to interact with shore after confirming no quarantinable disease aboard.
Regulatory detail & full definition
Requested via the Maritime Declaration of Health (form prescribed by IHR 2005). Granted electronically in most ports today; some still require physical health-officer boarding. Without free pratique, the yellow Q flag is flown and crew/cargo may not interact with shore. Port state control and customs can still board.
Source: International Health Regulations 2005 (WHO); FAL Convention